Autore:

Sahameddin Mahmoudi Kurdistani

Relatori:

Prof. Stefano Pagliara

Dott. Eng. Michele Palermo

Scour downstream of eco-friendly in-stream structures

Anno 2013

UNIVERSITÀ DI PISA

Scuola di Dottorato in Ingegneria “Leonardo da Vinci”

Corso di Dottorato di Ricerca in Scienze e tecniche dell’ingegneria civile

Tesi di Dottorato di Ricerca

SSD: ICAR/02 COSTRUZIONI IDRAULICHE E MARITTIME E IDROLOGIA

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SOMMARIO

Le “grade-control structures” (Cross-Vane, J-Hook vane, W-weir, Log vane, Block Ramps, ecc.) rappresentano un valido sistema per il controllo del trasporto solido di fondo e contribuiscono a creare habitat più favorevoli per le specie ittiche che popolano il corpo idrico. Esse hanno il vantaggio di minimizzare il loro impatto ambientale e allo stesso tempo non richiedono frequenti interventi antropici di manutenzione. Tuttavia, la presenza di tali opere contribuisce a modificare la morfologia del fondo, dal momento che sia fenomeni erosivi che formazione di dune hanno luogo a valle di esse. Pur essendo presenti in letteratura diversi criteri progettuali, ulteriori studi ed approfondimenti si rendono necessari al fine di ampliare e precisare il quadro conoscitivo. Pertanto, oggetto di questa tesi è lo studio, mediante sperimentazione di laboratorio, del processo erosivo a valle di Cross-Vane, J-Hook vane e W-weir. In particolare, la morfologia dello scavo e la formazione delle dune è stata approfondita ed analizzata. I dati sperimentali sono stati elaborati e relazioni analitiche sono state dedotte. Queste ultime possono costituire un valido supporto alla progettazione di tali tipologie strutturali. ABSTRACT

Eco-friendly in-stream grade-control structures [i.e. Cross-Vane, J-Hook vane, W-weir, Log vane, Block Ramps, etc.] represent a valid system both to control bed sediment transport and to create suitable habitat for fish species. They have the advantage to minimize their impact and at the same time they do not require frequent human intervention, such as dredging. Nevertheless, the free surface flow causes scour hole and dune downstream of them, contributing to change river morphology. In technical literature, there are several criteria to design them, but they are not complete and require a further development. Thus, this thesis aims to experimentally analyze the erosive process downstream of Cross-Vane, J-Hook vane and W-weir, in order to highlight the parameters affecting the phenomenon and furnish tools for a correct design. In particular, scour morphology and dunes formations have been investigated. Experimental data were analyzed and empirical relationships were derived to predict the main lengths of the scour hole and dune. The proposed equations can be useful for practical applications.

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INDEX

SOMMARIO .................................................................................................. 1

ABSTRACT ................................................................................................... 1

INDEX ........................................................................................................... 2

LIST OF SYMBOLS ..................................................................................... 4

LIST OF FIGURES ...................................................................................... 5

1 . INTRODUCTION .................................................................................... 8

1.1. River Restoration ................................................................................ 8

1.2. Grade-Control Structures. .................................................................. 9

1.2.1. Design Criteria and Features of Eco-Friendly Structures ....... 10

1.2.1.1. Boulder Placement ........................................................... 10

1.2.1.2. Log Vane ........................................................................... 13

1.2.1.3. Rock Vane ......................................................................... 16

1.2.1.4. Step Pools – Riffles ........................................................... 19

1.2.1.5. Cross-Vane ........................................................................ 21

1.2.1.6. J-Hook Vane ..................................................................... 23

1.2.1.7. W-Weir .............................................................................. 25

1.3. Literature Review .............................................................................. 27

2. EXPERIMENTAL SETUP AND INSTRUMENTS .............................. 29

2.1.Experimental Facilities ..................................................................... 29

2.1.1. Setup I ......................................................................................... 29

2.1.2. Setup II ....................................................................................... 34

2.1.3. Setup III ...................................................................................... 38

2.2. Instrumentation ............................................................................... 40

2.2.1 Point Gauge ................................................................................. 40

2.2.2 Ultrasonic distance measuring sensors ...................................... 40

2.2.3 Magnetostrictive Linear Position Transducer (GEFRAN) ...... 41

3. DIMENSIONAL ANALYSIS ................................................................. 42

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4. EXPERIMENTAL RESULTS AND DISCUSSIONS ........................... 45

4.1 Scour typology .................................................................................... 45

4.1.1 Cross-Vane Scour typology ......................................................... 45

4.1.2 J-Hook Vane Scour typology ...................................................... 48

4.1.3 W-wier Scour Typology ............................................................... 50

4.1.4 Conclusion ................................................................................... 50

4.2 Maximum Scour Depth ..................................................................... 52

4.3 Maximum Scour Lentgh .................................................................... 55

4.4 Maximum Scour Width ..................................................................... 57

4.5 Maximum Scour Location ................................................................. 59

4.6 Maximum Ridge Heigth and Length ................................................ 60

4.7 Detail Study on W-weir with Top-Openings ..................................... 61

3.7.1 Effect of Top-Openings on Maximum Scour Depth .................. 62

3.7.2 Effect of Top-Openings on Maximum Scour Location ............. 62

5. CONCLUSION ........................................................................................ 64

REFERENCES ........................................................................................... 66

ACKNOWLEDGMENTS

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LIST OF SYMBOLS

B channel width d50 mean particle diameter f functional symbol Fd densimetric Froude number = Q/{l·hst[g(Gs-1)d50]

0.5} g gravitational acceleration Gs ρs /ρ hst height of the structure (average height of the stones) l length of the structure lm scour length l’m ridge length Q flow discharge Q’ effective flow discharge = (b/B)Q S0 channel bed slope w the maximum development of the scour width x distance in longitudinal scour and ridge profiles xm location of the maximum scour depth y distance in latitude of channel y0 approach flow depth z elevation zm maximum scour depth z’m maximum ridge height Δy difference between water surface upstream and downstream of the structure structure arm angle width of each opening Φ, Φ’ functional symbol η Fd

2·Δy/hst ρ water density ρs bed material density σ particle uniformity factor = (d84/d16)

0.5

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LIST OF FIGURES

Fig. 1 Boulder placement ........................................................................................ 11 Fig. 2 Plan view of Boulder Placement detail (Rosgen 1996) ................................ 12 Fig. 3 Log-vane installed at Jocko River in USA.………………...……..………….. 13 Fig. 4 a) Plan and section view of Log-Vane, b) Alternative vane configurations (Hey 1995). ............................................................................................................. 15 Fig.5 Rock-vane ...................................................................................................... 16 Fig.6 Riprap diameter as a function of stream velocity (Based on Ishbash equation) ................................................................................................................. 17 Fig.7 a) Plan and section view of Rock-Vane , b) Rock-Vane profile view (Rosgen 1996) ........................................................................................................ 18 Fig. 8 Pool below riffles........................................................................................... 19 Fig. 9 a,b) Riffles profile view , c) Riffles plan view,(Rosgen 1996) ....................... 20 Fig. 10 cross-vane .................................................................................................. 21 Fig. 11 Plan and profile and cross section view of Cross-Vane (Rosgen 2001)...………………...…………………………………………………………...……22 Fig. 12 Contour map of Cross-Vane following major flood – San Juan River, 1996 ........................................................................................................................ 23 Fig. 13 J-Hook vane ................................................................................................ 23 Fig.14 Plan and profile and cross section view of J-Hook Vane (Rosgen 2001) ... 24 Fig. 15 W-weir ......................................................................................................... 25 Fig. 16 Plan and profile and cross section view of W-weir (Rosgen 2001) ............ 27 Fig. 17 a) Upstream and b) downstream view of experimental channel steup I .... 29 Fig. 18 Schematic diagram of experimental channel steup I.................................. 30 Fig. 19 Cross-Vane during test run ......................................................................... 30 Fig. 20 Plan and stream wise view of the channel with the main parameters of flow and scour for (a) I-shape structure;(b) U-shape structure............................... 31 Fig. 21 Plastic bed material .................................................................................... 31 Fig. 22 Schematic diagram of the experimental channel steup II .......................... 34 Fig. 23 plan, two streamwise views ,A-A, C-C and a cross section D-D of J-Hook 35 Fig. 24 J-Hook vane during test run ....................................................................... 35 Fig. 25 Granulometry of the bed material ............................................................... 37 Fig. 26 Plan view and cross sections of a) W-weir b) W-weir with openings ......... 38 Fig. 27 an upstream view of the W-weir structure before the test run .................... 39 Fig. 28 point gauge and in inset the vernier showing 0.1 mm precise ................... 40 Fig. 29 Ultrasonic Baumer ...................................................................................... 40 Fig. 30 compaison of the manual measurements versus ultrasonic sensor… ....... 41 Fig. 31 Magnetostrictive Linear Position Transducer (GEFRAN) ........................... 41 Fig. 32 Scour types (a) Type 1 for U-shape structure with l/B = 2.3, Fd = 1.28, ∆y/hst = 0.125 and S0 = 0. Elevation 32 is the initial channel bed level; (b) Type 2 for U-shape structure with l/B = 2.3, Fd = 0.96, ∆y/hst = 0.15 and S0 = 0; (c) Type 3 for U-shape structure with l/B = 1.7, Fd = 1.17, ∆y/hst = 0.2 and S0 = 0 .......................... 46 Fig.33 (a) scour typology for I-shape structure with l/B = 1 and, S0 = 0; (b) variation of types of scour for U-shape structure with l/B = 1.7, S0 = 0; (c) scour typology for U-shape structure with l/B = 2.3, S0 = 0; (d-f) scour formation for U-shape structure with l/B = 2.3 for different bed slopes (d) S0 = 0.01; (e) S0 = 0.025; and (f) S0 = 0.05 ................................................................................................................................ 47

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Fig. 34 Comparison of the ridge profiles for different scour types. ......................... 47 Fig.35 (a) scour Type 1 for J-Hook structure with b/B = 0.6, Fd = 2.05, ∆y/hst = 0.233 on horizontal channel bed; (b) scour Type 2 for J-Hook structure with b/B = 0.6, Fd = 1.23, ∆y/hst = 0.17 on horizontal channel bed; (c) scour Type 3 for J-Hook structure with b/B = 0.5, Fd = 1.14, ∆y/hst = 0.13 on horizontal channel bed. The reference bed level is 308 mm ............................................................................... 49 Fig. 36 Scour typology for J-Hook vane. … ............................................................ 50 Fig. 37(a) illustrates scour Type A for W-weir with l/B = 2.55, Fd = 0.338, ∆y/hst = 0.667 and η = 0.076 on horizontal channel bed. The elevation of 0 mm is the initial channel bed level (b) represents scour Type 2 for W-weir with b/B = 2.55, Fd = 0.513, ∆y/hst = 0.398 and η = 0.105 on horizontal channel bed. Finally and (c) shows scour Type C for W-weir with b/B = 2.55, Fd = 1.095, ∆y/hst = 0.147 and η =0.177 on horizontal channel bed. ......................................................................... 51 Fig. 38 Scour and dune formation during test run for W-weir ................................. 51 Fig.39 Comparison of Eq. (9) for various values of S0 and l/B with collected data and Scurlock et al. (2012) data; [−••−••−] l/B = 2.3 & S0 = 0.05, [---------] l/B = 2.3 & S0 = 0, [───] l/B = 1.3 & S0 = 0.0021 and [−−−−] l/B = 1 & S0 = 0. ....................... 52 Fig.40 Comparison of observed scour depths versus calculated zm /hst by Eq. (9) for current experimental study data. ....................................................................... 52 Fig.41 Comparison of Eq. (10) with observed data … ........................................... 53 Fig.42 Comparison of observed scour depths versus calculated zm /hst by Eq. (10)for current experimental study data and Scurlock et al. 2012 data … ............. 53 Fig.43 W-weir data classified by l/B and htw/hst… … .............................................. 54 Fig.44 Plan view of the scour and dune formation downstream of W-weir … ........ 54 Fig.45 Upstream view of the scour and dune formation downstream of W-weir … 54 Fig.46 Comparison of Eq. (12) for various values of S0 and l/B with collected data; [−••−••−] l/B = 2.3 & S0 = 0, [───] l/B = 2.3 & S0 = 0.025, [------] l/B = 1.7 & S0 = 0, [― ― ―] l/B = 2.3 & S0 = 0.05 and [••••••••]…........................................................ 55 Fig.47 Comparison of observed maximum scour lengths versus calculated lm /hst by Eq. (12) for current experimental study data l/B = 1 & S0 = 0. ............................... 56 Fig.48 Comparison Observed maximum scour lengths data for J-Hook vane for l/B=1 & S0=0 with Eq. (13)…………………………………………………………….. . 56 Fig.49 Comparison of observed scour length versus calculated lm /hst by Eq.(13)…………………………………………………………………………………….57 Fig.50 Classification of observed scour length data by l /B……………………….. . 57 Fig.51 Comparison of Eq. (14) for various values of l/B with collected Cross-Vane data in the horizontal channel bed condition………………………………………….58 Fig.52 Comparison of Eq. (15) with collected J-Hook vane data in the horizontal channel bed condition …………………………………………………………………..58 Fig.53 Longitudinal scour profile patterns of the channel for different l/B………… 59 Fig.54 Comparison of Eq. (16) for various values of l/B with collected data (independent of S0); [−••−••−] l/B = 1, [───] l/B = 1.7, [------] l/B = 2.3………… .... 59 Fig.55 Comparison of observed locations of the scour depths versus calculated xm /hst by Eq. (16) for current experimental study data ……………………..………… 59 Fig.56 Scour side view downstream of the I-shape structure …………………… ... 60 Fig.57 Non-dimensional longitudinal scour profiles for different approach Froude numbers …………………… .................................................................................... 60 Fig.58 Comparison of Eq. (17) with observed height of the dune for J-Hook Vane …………………… ................................................................................................... 61

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Fig.59 Comparison of Eq. (18) with observed length of the dune for J-Hook Vane… ………………………………………………………………………………………..… ... 61 Fig.60 Classification of observed scour depth data downstream of open W-weir by δ /B…………………………………………………………………. …………………… 62 Fig.61 Comparison of dimensional longitudinal profiles for closed W-weir and open W-weir for Q=25 l/s. …………………………………………………………………..…63 Fig.62 Comparison of dimensional longitudinal profiles for closed W-weir and open W-weir for Q=10 l/s. …………………………………..…………………………………63 LIST OF TABLES Table 1 Classification Key for Natural Rivers (Rosgen 1996) ............................... 10 Table 2 Cross-Vane data test range ...................................................................... 32 Table 3 J-Hook Vane data test range ..................................................................... 36

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1. INTRODUCTION 1.1. River Restoration

Restoring a river is analogous to healing a patient. The human body is comprised of interacting systems and organs that work collectively to determine the overall health of the individual. Like the human body, the health of a river is dependent on interacting systems. Hydraulics, hydrology, geomorphology, water quality, and biology are components of rivers that work collectively to define rivers and their health. Each of these components is, in itself, a complex group of variables. Changes in one of these components can have a cascading effect on the others. Stream restoration or river rehabilitation, sometimes called river reclamation, describes a set of activities that help to improve the environmental health of a river or stream. Improved health could be indicated by expanded habitat for diverse species such as fish and other aquatic wildlife and reduced stream bank erosion. Enhancements may also include improved water quality (i.e. reduction of pollutant levels and increased dissolved oxygen levels) and achieving a self-sustaining, functional flow regime in the stream system that does not require periodic human intervention, such as dredging or construction of flood control structures. Stream restoration projects can also yield increased property values in adjacent areas.

River restoration projects aim to increase ecosystem goods and services, and ideally convert damaged freshwater systems into sustainable ones whilst protecting downstream and coastal ecosystems (Palmer et al. 2005). River rehabilitation can be passive, where we simply allow natural hydraulic forces to reshape rivers slowly and reinstate the natural heterogeneity (Gillilan et al. 2005). Alternatively, we can apply specific and active measures more rapidly to modify channel form and structure or to reintroduce variations in stream flow, recognizing that river systems are naturally dynamic.

One of the most challenging problems facing river engineers today is the stabilization of degrading channels. Channel degradation leads to damage of both riparian infrastructure, as well as the environment. Bank protection is generally ineffective over the long term and will probably be a waste of resources if the channel continues to degrade. When systemwide channel degradation exists, a comprehensive treatment plan is usually required. A wide variety of structures has been employed to provide grade control in channel systems.

River restoration based on the principles of the the natural channel design approach (Rosgen 2001) geomorphic channel design approach is most commonly accomplished by restoring the dimension, pattern, and profile of a disturbed river system by emulating the natural, stable river. Restoring rivers involves securing their physical stability and biological function, rather than the unlikely ability to return the river to a pristine state. The natural channel design approach involves the use of reference channel morphology and grade-control structures as templates for design. Reference channels are selected for their natural stability, habitat, and functions. Normally, these reference channels are least altered reaches found on the same river where the restoration is proposed. The logic of this approach is that reference reaches within the same watershed and with similar drainage area are handling the flows and sediment that the restored channel will need to carry. In addition, mimicking habitat characteristics in a natural reference channel is more likely to address habitat needs of the biota found there. In adapting reference channel morphology to restoration sites, slope differences, sediment differences, sediment transport capacity and competence, and flow capacity must be accounted for.

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1.2. Grade-Control Structures

Modifications to a stream channel may be appropriate to address degradation. Channel modifications may yield improved habitat for wildlife and plants in a stream corridor, but can result in flooding, excessive erosion or other damage if not carefully planned. Design of modifications involves a careful analysis of a complex fluvial processes. Alterations may include channel shape (in terms of sinuosity and meander characteristics), cross-section and channel profile (slope along the channel bed). Alterations affect the dissipation of energy through the channel, which has an impact on stream velocity and turbulence, sediment volume and size distribution, scour, and water surface elevations, among other characteristics.

Grade control is an essential component to stabilize a degrading stream or one that is subject to conditions that may cause degradation. Channel degradation leads to damage of bridges, culverts, petrochemical transmission lines, power lines, sewer and water lines, and other infrastructure. Channel degradation produces an overheightened and oversteepened condition of the channel banks that often leads to severe mass failures of both streambanks. The resulting channel widening and bank erosion cause severe land loss and damage to riparian infrastructure and habitat.

As channel degradation continues, the ground water table may also be lowered along the stream, affecting riparian vegetation. Sediment eroded from the degrading channels is transported downstream, adversely impacting flood control channels, reservoir areas, and wetland habitat areas. This sediment also carries significant amounts of nutrients, particularly phosphorus, which may degrade water quality and habitat along the stream system. Consequently, channel degradation is not simply a local problem that only affects a few landowners, but rather, produces systemwide consequences that can impact all taxpayers.

When systemwide channel degradation exists, a comprehensive treatment plan is usually required. This treatment plan usually involves the use of one or more grade- control structures to arrest the degradation process. In the widest sense, the term grade control can be applied to any alteration in the watershed that provides stability to the streambed. It can include stream realignments. The most common method of establishing grade control is the construction of in-stream grade control structures. A wide variety of grade-control structures has been used in channel systems. These treatments range from simple loose rock structures to reinforced concrete weirs and vary in scale from small streams to large rivers.

The two primary engineering factors that promote channel stability are continuity of water and sediment through the stream reach and geotechnical bank stability. A series of well-designed grade-control structures can adjust sediment transport capacity to sediment supply and can improve bank stability by reducing bank height and reducing shear at the bank toe. In addition to the methods used to reference channel morphology, significant discussion of the design approach has focused on its heavy use of eco-friendly in-stream structures such as Cross-Vanes, J-Hook Vanes, Single-Arm Vanes, and W-weirs (Miller and Kochel 2009; Puckett and Jennings 2007). These structures are used to either temporarily lock the channel in place by limiting bed and bank erosion until the riparian vegetation can become re-established or create a stable (static) channel where infrastructure needs to be protected. In both cases, in-stream structures are also intended to serve as

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habitat improvement devices by increasing the complexity of the channel bed as well as the river’s local flow conditions.

1.2.1. Design Criteria and Features of Eco-Friendly Structures

The intent of this part is to address a wide range of common biotechnical engineering techniques and conventional, hard engineering solutions including the effective uses and limitations, material specifications, and installation details. Throughout the design criteria, where applicable, the stream types for which the practices are appropriate are given in terms of the Rosgen classification scheme (see Table 1).

Table 1 Classification Key for Natural Rivers (Rosgen 1996)

* Entrenchment ratio = flood-prone area width/bankfull width

1.2.1.1. Boulder Placement

This arrangement consists of placing boulders in stream channels to encourage riffles and pools and to provide habitat and spawning areas for aquatic life (see Fig. 1). When properly utilized, boulder placements create small scour pools and eddies which can be used as rearing areas for salmonids and other fish. Additionally, they are sometimes used to restore meanders and pools in channelized reaches and to protect eroding streambanks by deflecting flow.

*

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Fig. 1 Boulder placement

Boulder placements are most effective when used in the following conditions:

moderately wide, shallow, high velocity streams with gravel or cobble beds;

stream reaches with pool densities less than 20 percent; and

Rosgen stream types B3 and B4 (table 1).

Boulder placements should be avoided in the following areas:

channels which do not have sufficient particle size ranges to develop armor layers such as streams with fine, noncohesive bed material such as sand or small gravel that will scour deeply and rapidly, thereby undermining and burying boulder groups,

channels with highly erodible embankment soils or soils with an extreme excess of one texture or size range unless measures are taken to adequately reinforce the banks;

low-velocity streams with a mean velocity of less than about 0.6 meters per second, since sufficient scour pools cannot be developed;

newly formed stream curvatures since boulder clusters can alter natural patterns of stream meander resulting in erosion and scour problems;

Overwide streams or streams with large bedload.

Boulders should be chosen based upon stream size, flow characteristics, bed stability, desired habitat effects such size and position of resultant scour pools and eddies, and the

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capacity of available heavy equipment. Boulder diameters of 0.6 to 1.5 meters and volumes of 1 to 2 cubic meters have been suggested for this restoration practice. However, boulders should not be more than 25 to 30% of bankfull depth after partial embedment. Blocky, angular rock should be used in place of round rock when feasible. Boulder diameters should be no more than 1/8 the width of the stream. If a larger size is to be used, bankstabilization measures should be considered.

All erosion and sediment control devices, including dewatering basins, should be implemented as the first order of business according to a plan approved by the WMA or local authority. Boulder placement should proceed as follows (Fig. 2):

1) Complete the work during periods of low flow to ensure proper location within the stream channel and to facilitate the movement of heavy equipment.

2) Boulders shall be placed on top of footer rocks(s) so that the boulder is offset in the upstream direction.

3) Place clusters comprised of 3 to 5 boulders arranged in a triangular configuration in the downstream half of long riffles, sufficiently far from the associated pool, and embed them in the stream bed to increase the cluster’s stability. The substrate in which boulders are placed should be competent enough to resist undercutting.

4) Space multiple boulder clusters constructed in the same stream section a minimum of 1/3 of a stream width apart. Avoid an overabundance of newly placed boulders since this can inhibit the natural process of sediment flushing.

Fig. 2 Plan view of Boulder Placement detail (Rosgen 1996)

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1.2.1.2. Log Vane

This instalation consists of installing log vanes to direct normal flows away from unstable stream banks and to improve and create aquatic habitat by enhancing flow diversity through the formation of scour pools.

Log vanes are single-arm structures which are partially embedded in the streambed such that they are submerged even during low flows. When properly positioned, log vanes induce secondary circulation of the flow thereby promoting the development of scour pools (Fig. 3).

Fig. 3 Log-vane installed at Jocko River in USA.

Log vanes can also be paired and positioned in a channel reach to initiate meander development or migration. Additionally, the following limitations apply to log vanes:

1) Vanes should be used carefully in vertically unstable streams unless measures have been taken to promote stream stability so that it may retain a constant planform and dimension without signs of migration or incision

2) Vanes are ineffective in bedrock channels since minimal bed scouring occurs. Conversely, log vanes should be used carefully in streams with fine sand, silt, or otherwise unstable substrate since significant undercutting can destroy these measures.

3) Vanes should not be used in stream reaches which exceed a 3% gradient.

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4) Vanes should not be used in streams with large sediment or debris loads.

5) Vanes are best suited to Rosgen types B2-B5 and C2-C4 (table 1).

6) Banks opposite these structures should be monitored for excessive erosion.

Materials for vanes should meet the following requirements:

Logs: Single logs should be at least 20 to 25 centimeters in diameter. Smaller logs should be bolted securely together. Recommended construction requirements for log vanes are as follows (Fig. 4):

1. The stream should be diverted according to an approved practice, and the construction area should be dewatered.

2. Combinations of log vanes when placed to initiate meander development, should be spaced 5 to 7 stream bankfull widths apart and arranged on alternating banks. Vanes used for habitat creation should be spaced 1 or more channel widths apart depending upon the pattern of scour pools in natural reference reaches. Additionally, the following primary design criteria need to be satisfied: shape and orientation, height, and length.

Shape and orientation. Vanes should be angled 20 to 30 degrees from the upstream bank.

Height. The bank-end of the vane should be at the bankfull elevation and the tip of the vane should be partially embedded in the streambed such that it is submerged even during low flows. The vane should be placed at a vertical angle of 3% to 7%.

Length. Vanes should span a maximum of 1/3 of the channel width, depending on the channel size. Channels less than 20 feet may require a vane to extend 1/2 of the channel width. The larger the channel, the shorter the vane should be relative to the channel width.

3. When installing vanes, the bank end of the structure should be firmly anchored a minimum of 1.5 to 1.8 meters into the slope. When two or more smaller logs are used in place of one larger log, they should be anchored to each other with 0.9 meter rods of 1.3 to 1.6 cm diameters. The rods should be driven in until a 10 centimeter tail remains, which should be bent in a downstream direction.

When necessary, the logs may also be secured with cables. Log structures should be anchored to the stream bed with support pilings with lengths exceeding probable scour depths.

4. Large rocks can be positioned on the downstream face of the vanes to provide further stability.

5. All disturbed areas should be permanently stabilized in accordance with an approved sediment and erosion control plan.

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Fig. 4 a) Plan and section view of Log-Vane,

b) Alternative vane configurations (Hey 1995)

a)

b)

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1.2.1.3. Rock Vane

The design criteria and specifications of Rock-Vane structures are the same as Log-Vanes just instead of logs, are constructed with rocks. (Fig. 5)

Fig. 5 Rock-vane

Materials for vanes should meet the following requirements:

Large Rocks: Large rocks for vane construction should be sized to withstand the design flood according to Figure 6. In general, rock sizes should have a minimum of 2.5 median diameters or weigh a minimum of 200 pounds. Additionally, large rocks and boulders can be positioned on the downstream side of straight vanes to provide further stability.

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Fig. 6 Riprap diameter as a function of stream velocity (Based on Ishbash equation)

Slope Protection and Stabilization Techniques, MARYLAND Evvironment Waterway Construction Guidelines, 2000

When installing vanes, the bank end of the structure should be firmly anchored a minimum of 2-3 rocks into the bank. Figures 7(a) and 7(b) show the design view of Rock-Vane structures.

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Fig. 7 a) Plan and section view of Rock-Vane

b) Rock-Vane profile view (Rosgen 1996)

a)

b)

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1.2.1.4. Step Pools – Riffles

The work should consist of constructing step-pool sequences in steep headwater stream channels for grade control and the creation of aquatic habitat through flow diversification (Fig. 8). Step-pool channels are characterized by a succession of channel-spanning steps formed by large grouped boulders called clasts that separate pools containing finer bed sediments. As supercritical flow tumbles over the step, energy is dissipated in roller eddies and becomes subcritical in the associated downstream plunge pool.

Fig. 8 Pool below riffles

Step-pool morphologies are typically associated with well confined, high-gradient channels with slopes greater than 3%, having small width-depth ratios and bed material dominated by cobbles and boulders. Step pools generally function as grade control structures and aquatic habitat features by reducing channel gradients and promoting flow diversity. At slopes greater than roughly 6.5%, similar morphologic units termed cascades spanning only a portion of the channel width are formed in these channel conditions. Step pools and cascades are generally found in the following Rosgen stream types: A1-A3 and B1-B3.

Natural steps in riffle morphologies can be formed by large clasts, bedrock outcrops, and large woody debris aligned across the channel. Engineered steps can be made from boulders, logs, and large woody debris chosen according to the desired height of the step. Additionally, boulders should be sized to resist the design storm event.

The proposed construction sequence for step pools is as follows (fig. 9):

1. The stream should be redirected by an approved temporary stream, the construction area should be dewatered, and any disturbed banks should be stabilized.

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2. Step-pool units should be designed and constructed to have a characteristic step height, H, and step length, L, as shown in Fig. 9, and all steps should be firmly anchored into the stream bank.

3. Step rocks shall be placed on footer rocks so that they rest on two halves of each footer rock below, and so that the step rock is offset in the upstream direction. Footer rocks should extend below the scour hole elevation.

4. As a general guideline, the ratio of the mean steepness, defined as the averaged value of step height over step length, to the channel slope, S, should lie in the range of 1 to 2·(1·{(H/L)AVE/S}·2). Typical spacings for step pools and cascades are provided in Fig. 9(b) relating to alluvial channel morphologies.

5. Whenever practical, a reference reach with similar flow rates, bed and bank material characteristics, type and density of riparian vegetation, and channel gradient should be surveyed at low flows to determine appropriate values of H and L. At high discharges, step-pool characteristics may be obscured.

6. Once construction is completed, the diversion should be removed from upstream to downstream. Sediment control devices, including perimeter erosion controls, are to remain in place until all disturbed areas are stabilized in accordance with an approved sediment and erosion control plan and the inspection authority approves their removal.

(Abrahamas et al. 1995)

Fig. 9 a,b) Riffles profile view

c) Riffles plan view(Rosgen 1996)

c)

a) b)

21

1.2.1.5. Cross-Vane

The Cross-Vane is a rock grade control structure (Fig. 10) that decreases near-bank shear stress, velocity and stream power, but increases the energy in the center of the channel. The design of the Cross-Vane structure is shown in plan, profile and section view in Fig. 11. The structure will establish grade control, reduce bank erosion, create a stable width/depth ratio, maintain channel capacity, while maintaining sediment transport capacity, and sediment competence. The Cross-Vane also provides for the proper natural conditions of secondary circulation patterns commensurate with channel pattern, but with high velocity gradients and boundary stress shifted from the near-bank region.

Fig. 10 cross-vane

22

Fig. 11 Plan and profile and cross section view of Cross-Vane (Rosgen 2001)

The Cross-Vane is also a stream habitat improvement structure due to:

1) an increase in bank cover due to a differential raise of the water surface in the bank region;

2) the creation of holding and refuge cover during both high and low flow periods in the deep pool;

3) the development of feeding lanes in the flow separation zones (the interface between fast and slow water) due to the strong downwelling and upwelling forces in the center of the channel; and

4) the creation of fish spawning habitat in the tail-out or glide portion of the pool.

Major floods have tested the Cross-Vane structure such as the 1996 flood on the San Juan River in Pagosa Springs, which passed a flood stage of 3.5 meters above the top of the structures on a 0.005 slope. A detailed contour map prepared in 2000 demonstrates the channel shape and location of the deep pool (Fig. 12). The structure did require post-flood maintenance and it is still performing properly as a diversion structure, a kayak playground and an excellent fly-fishing location where fisherman can be frequently observed. Although bedload transport of particle size up to 220 mm occurred during the flood, the pools did not fill. The strong downwelling currents in the center of the channel maintained a high bedload transport keeping the pool deep as evidenced in Fig. 12 (Rosgen 2001).

23

Fig. 12 Contour map of Cross-Vane following major flood – San Juan River, 1996.

1.2.1.6. J-Hook Vane

J-hook vanes are single-arm structures whose tip is placed in a “J” configuration and partially embedded in the streambed such that they are submerged even during low flows (Fig. 13). When properly positioned, J-hook vanes induce secondary circulation of the flow thereby promoting the development of scour pools. J-hook vanes can also be paired and positioned in a channel reach to initiate meander development or migration.

Fig. 13 J-Hook vane

24

Additionally, the following limitations apply to J-hook vanes:

1) J-hook vanes should not be used in unstable streams unless measures have been taken to promote stream stability so that it may retain a constant planform and dimension without signs of migration or incision

2) J-hook vanes are ineffective in bedrock channels since minimal bed scouring occurs. Conversely, streams with fine sand, silt, or otherwise unstable substrate should be avoided since significant undercutting can destroy these measures.

3) J-hook vanes should not be used in stream reaches which exceed a 3% gradient.

4) J-hook vanes should not be used in streams with large sediment or debris loads.

5) J-hook vanes are best suited to Rosgen types B2-B5 and C2-C4 (Table 1).

6) Banks opposite these structures should be monitored for excessive erosion.

Materials for vanes should meet the following requirements:

Large Rocks: Large rocks for vane construction should be sized to withstand the design flood according to Fig. 6. In general, rock sizes should have a minimum of 2.5 median diameters or weigh a minimum of 200 pounds. Footer rocks should be long and flat.

Recommended construction requirements for J-hook vanes are as follows (refer to Fig. 14):

1. The stream should be diverted according to an approved practice, and the construction area should be dewatered.

2. When placed to initiate meander development, vanes should be spaced 5 to 7 bankfull widths apart and arranged on alternating banks. Vanes used for habitat creation should be spaced 1 or more channel widths apart depending upon the pattern of scour pools in natural reference reaches. Additionally, the following primary design criteria need to be satisfied: shape and orientation, height, and length.

Fig. 14 Plan and profile and cross section view of J-Hook Vane (Rosgen 2001)

25

Shape and orientation. Vanes should be angled 20 to 30 degrees from the upstream bank.

Height. The bank-end of the vane should be at the bankfull elevation and the tip of vane should be partially embedded in the streambed such that it is submerged even during low flows. This tip should be placed to form a semi-circular structure at the streambed. The vane arm should be placed at a vertical angle of 3% to 7%.

Length. Vanes should span a maximum of 1/3 of the channel width, depending on the channel size. J-hooks may span up to 60% of the channel width. The larger the channel, the shorter the vane should be relative to the channel width.

3. When installing vanes, the bank end of the structure should be firmly anchored a minimum of 1-2 rocks into the bank.

4. Vane rocks should be placed on top of footer rocks such that each vane rock touches adjacent rocks and rests upon two halves of each footer rock below it, and so that the vane rock is offset in the upstream direction. Vane rocks shall be shingled upstream.

5. All disturbed areas should be permanently stabilized in accordance with an approved sediment and erosion control plan.

1.2.1.7. W-Weir

Low profile in-stream structures such as w-weirs are primarily used to create aquatic habitat in the form of scour pools and for grade control on incising streams and rivers. Additionally, they are well-suited for channeling flow away from unstable banks (Fig. 15).

Fig. 15 W-weir

26

W-weirs are typically suited for use in moderate to high gradient streams and best suited for types B3-B4, C3-C4, and F3-F4. Additionally, w-weirs are best used in rivers with bankfull widths greater than 40 feet (12 meters). When constructed and spaced properly, weirs can simulate the natural pattern of pools and riffles occurring in undisturbed streams while forming gravel deposits which fish use as spawning grounds. W-weirs can also be used to stabilize banks when designed properly. W-weirs should be avoided in channels with bedrock beds or unstable bed substrates, and streams with naturally well developed pool-riffle sequences.

Rock and boulder material for the construction vortex weirs and w-weirs should meet the following requirements:

Vortex and Footer Rocks: Vortex rocks should be large enough to achieve the desired height when partially buried in the stream bed and should be sized to resist movement from shear stresses expected for the design flow. Footer rocks should be long and flat.

Riprap: Riprap for added stability, bank armoring, and toe protection should be capable of withstanding bankfull flow velocities according to Fig. 6.

The recommended construction weirs should proceed as follows (Fig. 16):

1. The stream should be diverted according to a WMA recommended measure, and the construction area should be dewatered.

2. Vortex Rock Weir Installation. Vortex weirs are typically modified horseshoe shapes such that the apex of the structure points upstream. The angle the arms make with the upstream bank should be approximately 20 to 30 degrees so that flows are directed away from the banks and deeper pool areas are created directly downstream of the vane or weir. The top layer of vortex rocks should rest upon at least one tier of footer rocks and so that they are offset in the upstream direction. Vortex rocks should be partially buried in the streambed a minimum of 6 inches (15 centimeters). Vane rocks should be shingled upstream. On unstable bed substrates, two tiers of footer rocks may be required to prevent the downstream face of the vortex weir from being undermined. The top elevation of the center vortex rock(s) at the apex of the weir should be at or near bed level to permit fish passage at low flows, and the end rocks on either bank should be at bankfull level. The vortex rocks of vortex weirs should be spaced 1/3 to 1/2 a rock diameter apart with the exception of the end rocks. The end vortex rocks should be partially buried in the streambank and should touch the adjoining vortex rocks. Once the excavated portion of the bank has been backfilled, it should be armored with appropriately sized riprap, sod mats, or willow transplants as necessary.

27

Fig. 16 Plan and profile and cross section view of W-weir (Rosgen 2001)

3. W-Weir Installation. W-weir installation should proceed similarly to vortex weir construction and should account for the more complicated geometry of the structure.

4. Adjacent weirs should be spaced sufficiently far apart to allow for proper riffle or pool development according to step-pool and pool-riffle configurations as provided in MGWC 3.9: Step Pools. Additionally, it has been recommended that the overall drop controlled by a set of weirs should be less than 2 feet (0.6 meters) for stability reasons.

5. All disturbed sections of the channel, including the banks and streambed, should be stabilized with methods approved by the WMA.

6. All weirs should be monitored to determine if:

their orientation and geometry (e.g., the height of the drop) hinder fish migration,

their performance is adversely affected by deposited sediment, and

their placement causes bank instabilities and undesirable lateral stream movement especially in the vicinity of the plunge pools.

1.3. Literature Review

The physical and biological manipulation of stream channels to improve aquatic and riparian health has increased exponentially since the early 1990's (Bernhardt et al. 2005). Few experimental studies on grade-control structures are presented in literature. Bormann and Julien (1991) conducted a series of experiments including 231 scour depth measurements. They used steel plate for making the grade-control structure and downstream face of the structure was formed in different slopes, vertical, 1:1 (V:H) and 1:3 (V:H). They used the scour depth equation form proposed by Mason and Arumugan (1985)

28

and showed that large-scale experiments extend the range of available local scour data including vertical jets, wall jets, free over-fall jets, submerged jets and flow over grade-control structures. Shields et al. (1995) arranged a field measurement study on 1 km long reach of Goodwin Creek stream in north-west Mississippi. They investigated the effects of stone grade-control structures that were constructed for fish migration. D’Agostino and Ferro (2004), based on dimensional analysis and experimental data found a unique parameter that can estimate approximately the maximum scour depth. This unique parameter was the ratio of the total head over the structure by the drop height. Ben Meftah and Mossa (2006) studied the effects of bed sills on scour geometry and found that the maximum scour depth and the length of the scour depend on the distance between sills. They presented two simplified formulas to estimate the maximum scour depth and the length of the scour hole. A series of experiments and analysis of the scour process downstream of an apron was conducted, by Dey, S. et al. (2003-2008). In particular, Dey and Westrich (2003) carried out experiments in the presence of a cohesive bed downstream of an apron. The authors presented a complete and detailed analysis of the phenomenon considering the time evolution of the scour hole. Dey and Sarkar (2008) developed experiments on the submerged jets characteristics downstream of an apron. They showed that the flow in the scour hole is self-preserving as confirmed also by Pagliara et al. (2012b).

Rosgen (2001) presented a series of grade control structures including J-Hook. This type of vane is an open hydraulic structure with no obstruction for fish migration and is a high eco-friendly structure. In particular, in the last decades, low-environment impact structures, such as block ramps, have received a great attention. Namely, Pagliara (2007) derived simple equations to predict the scour depth and length carrying out a series of tests on scour downstream of block ramps in clear water condition and free hydraulic jump in mobile bed. He found that both the scour depth and length are function of ramp slope, densimetric Froude number and sediment non-uniformity parameter. The analysis of scour morphology was further developed by Pagliara and Palermo (2008a, 2008b) and Pagliara et al (2009), including the effect of protection sills in the stilling basin for different bed materials. Nevertheless, only recently, the influence of stilling basin geometry on both the erosive process and flow characteristics downstream of block ramps has been analyzed (Pagliara and Palermo 2010, 2011a, 2011b). However, relatively few studies are present in literature dealing with localized scour phenomena downstream of block ramps for live-bed conditions (see Pagliara et al. (2011, 2012a)).

Bhuiyan et al. (2007) studied the scour development downstream of W-weirs. Scurlock et al. (2011) developed one-dimensional model to predict Energy dissipation in U-Weir grade-control structures. Scurlock et al. (2012) focused on maximum velocity effects from Vane-Dike installations in channel bends and found a series of equations which represent maximum changes in flow velocities at the outer-bank, inner-bank, and centerline locations within a channel bend from the installation of vane-dike fields. Scurlock et al. (2012) contributed to conduct experimental study on scour downstream of grade-control structures. They carried out a series of 27 experiments to evaluate the main scour geometry parameters downstream of three different types of grade-control structures A, U and W.

This study aims to experimentally analyze the scour formation and classification downstream of three different types of eco-friendly in-stream grade-control structures; Cross-Vane, J-Hook Vane and W-weir.

29

2. EXPERIMENTAL SETUP AND INSTRUMENTS

2. 1. Experimental Facilities

All the experiments for the present study were conduted in two channels setup made in the Hyadraulic Laboratory (PITLAB) of Department of Energy Engineering, Systems, Land and Construction, University of Pisa. Channel setup I was used to study the scour parameters downstream of Cross-Vane structures and channel setup II was used to study the scour phenomena downstream of J-Hook vane and channel setup III for W-weir structures.

2.1.1. Setup I

The channel setup I included a horizontal rectangular channel 0.342 m wide, 7.00 m long and 0.63 m high (Fig. 17). Glass sidewalls enable to see the flow properties. An overhead tank (1.00 m deep and of surface area 1.00 m × 1.00 m) supplied stable inflow. A magnetic current meter measured the discharge in precision of ±0.010 l/s. The water surface profiles were measured using a point gauge of reading accuracy of ±0.1 mm. Figure 18 shows the schematic diagram of the experimental setup, where water is pumped from a rectangular tank to an overhead tank. This is provided inorder to make the inflow smooth and less turbulent. Figure 19 showes a Cross-Vane in experimental channel setup I during test run.

Fig. 17 a) Upstream and b) downstream view of experimental channel setup I.

(a) (b)

30

Fig. 18 Schematic diagram of experimental channel setup I

Fig. 19 Cross-Vane during test run

Fig. 20 shows the plan and stream wise view of the channel with the main parameters of the flow and the scour for (a) I-shape structure; (b) U-shape structure, where B is the channel width, y0 is the approach flow depth, hst is the height of the structure (defined as the average height of the stones top), Δy is the difference between water surface upstream and downstream of the structure, zm is the maximum depth of scour, lm is the scour length, z'm is the maximum height of the ridge, l'm is the ridge length, l is the length of the structure, xm is the location of the maximum scour, w is the maximum development of the scour hole width and S0 is the channel bed slope. The test ranges are shown in Table 2. The densimetric particle Froude number is Fd = Q/{l·hst[g(Gs-1)d50]

0.5} where Q is the flow discharge,

31

Gs= ρs /ρ, in which ρs = bed material density and ρ = water density, d50 is the mean particle diameter and g = gravitational acceleration. One uniform plastic material was used for channel whose Gs = 1.29 and d50 = 3.52 mm (Fig. 21) which has practically the same non-dimensional Shields parameter of sand with Gs = 2.44 and d50 = 1 mm (Pagliara and Carnacina 2011). At the beginning of each experiment, the channel bed was carefully leveled. Two series of experiments were carried out. The first series included tests on I-Shape structure with l/B = 1 and U-Shape structure with l/B = 1.7 and 2.3 for different values of the structure height, discharge and Δy in horizontal channel bed. The second series of experiments included I-Shape structure with l/B = 1 in a channel with S0 = 5% And U-Shape structure with l/B = 2.3 in a channel with S0 = 1, 2.5 and 5%.

Fig. 20 Plan and stream wise view of Fig. 21 Plastic bed material the channel with the main parameters of flow and scour for (a) I-shape structure; (b) U-shape structure

32

Test No. Structure Type Q (m3/s) S0 l/B ∆y (m) hst (m) Fd zm (m)

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

I I I I I I I I I I U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U U

0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0020 0.0030 0.0030 0.0020 0.0030 0.0020 0.0030 0.0040 0.0030 0.0040 0.0020 0.0020 0.0030 0.0030 0.0020 0.0030 0.0020 0.0030 0.0030 0.0040 0.0040 0.0040 0.0020 0.0040 0.0050 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0020 0.0020 0.0020 0.0020 0.0030

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.010 0.010 0.010 0.010 0.010 0.010 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28

0.0070 0.0040 0.0040 0.0080 0.0030 0.0030 0.0100 0.0180 0.0120 0.0170 0.0130 0.0100 0.0050 0.0100 0.0010 0.0020 0.0030 0.0030 0.0060 0.0050 0.0090 0.0040 0.0070 0.0090 0.0100 0.0060 0.0020 0.0050 0.0040 0.0010 0.0010 0.0010 0.0160 0.0110 0.0100 0.0070 0.0080 0.0050 0.0070 0.0060 0.0120 0.0150 0.0210 0.0280 0.0160 0.0240 0.0070 0.0100

0.030 0.030 0.030 0.030 0.020 0.020 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.020 0.020 0.020 0.030 0.030 0.030 0.030 0.030 0.030 0.040 0.040 0.040 0.040 0.040 0.040 0.020 0.020 0.020 0.040 0.040 0.030 0.030 0.020 0.020 0.020 0.020 0.020 0.020 0.020 0.020 0.030 0.030 0.030 0.030

1.95 2.92 1.95 2.92 2.92 4.38 1.46 1.46 2.19 2.19 0.88 1.31 0.88 1.31 3.51 2.63 3.51 1.17 1.17 1.75 1.75 0.85 1.28 0.64 0.96 0.96 1.28 1.28 1.28 1.28 2.56 3.20 0.64 0.96 0.85 1.28 1.28 1.92 1.28 1.92 1.28 1.92 1.28 1.28 0.85 0.85 0.85 1.28

0.0370 0.0390 0.0300 0.0540 0.0210 0.0390 0.0410 0.0540 0.0700 0.0800 0.0330 0.0370 0.0280 0.0330 0.0370 0.0170 0.0380 0.0380 0.0450 0.0450 0.0450 0.0470 0.0380 0.0470 0.0430 0.0360 0.0550 0.0530 0.0240 0.0080 0.0330 0.0300 0.0570 0.0730 0.0670 0.0700 0.0730 0.0580 0.1020 0.0890 0.1130 0.1310 0.1080 0.1310 0.1090 0.1500 0.0600 0.1440

Table 2 Cross-Vane data test range

33

Test No. Structure Type Q (m3/s) S0 l/B ∆y (m) hst (m) Fd zm (m)

49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU

I I I I I I

0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0030 0.0030 0.0020 0.0030 0.0020 0.0030 0.0040 0.0020 0.0030 0.0020 0.0030 0.0020 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020 0.0030 0.0030 0.0020 0.0030 0.0020 0.0030 0.0020

0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.025 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050

2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 2.28 1.00 1.00 1.00 1.00 1.00 1.00

0.0170 0.0190 0.0260 0.0270 0.0250 0.0310 0.0160 0.0190 0.0200 0.0260 0.0160 0.0130 0.0290 0.0300 0.0320 0.0470 0.0450 0.0690 0.0670 0.0240 0.0520 0.0530 0.0710 0.0640 0.0220 0.0260 0.0310 0.0330 0.0470 0.0430 0.0630 0.0570 0.0280 0.0420 0.0400 0.0350 0.0430 0.0400

0.030 0.030 0.030 0.030 0.040 0.040 0.040 0.040 0.040 0.040 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.020 0.020 0.020 0.020 0.020 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.040 0.030 0.030 0.020 0.020

0.85 1.28 0.85 1.28 0.96 0.96 0.64 0.96 0.64 0.96 0.85 1.28 0.85 1.28 1.71 0.85 1.28 0.85 1.28 1.28 1.28 1.92 1.28 1.92 0.64 0.96 0.64 0.96 0.64 0.96 0.64 0.96 1.46 2.19 1.95 2.92 2.92 4.38

0.1090 0.1290 0.1280 0.1510 0.1200 0.1670 0.0630 0.0930 0.0890 0.1200 0.1030 0.1240 0.1100 0.1520 0.2130 0.1810 0.1570 0.1780 0.2100 0.1090 0.1270 0.1850 0.1750 0.2030 0.0760 0.1110 0.0910 0.1150 0.1260 0.1520 0.1620 0.1900 0.1250 0.1830 0.1600 0.1850 0.1850 0.2050

Table 2 Cross-Vane data test range (continue)

34

2.1.2. Setup II

The experimental channel setup II included a horizontal rectangular channel 0.80 m wide, 20 m long and 0.75 m high with a part of 2 meters of a mobile horizontal bed (Fig. 22). An overhead tank supplied stable inflow. A standard weir measured the discharge in precision of ±0.1 l/s .The water surface profiles were measured using a point gauge of reading accuracy of ±0.1 mm. An ultrasonic “Baumer” sensor with precision of 0.001 m has been used for the bathymetry of the mobile bed at the end of the test and in the absence of water in the channel. Fig. 23 shows a plan, two streamwise views A-A, C-C and a cross section D-D of the channel with the main parameters of the flow and the scour. In fig. 23 α is the arm angle of the structure in respect to the river bank, l0 is the length of the arm of the structure, l2 is the length of top-part of the structure, l1= l0 sin α, b is the width of the structure, y0 is the approach flow depth, hst is the height of the structure (defined as the average height of the stones top) and to avoid the scale effect 4 different heights of structures were made using stones in average top heights of 21, 41, 62 and 92 mm. Δy is the difference between water surface upstream and downstream of the structure at the maximum scour depth, δ is the width of each top-opening of the structure, B is the channel width, zm is the maximum depth of the scour downstream of the J-Hook vane, z*m is the maximum scour depth at the end of the top-part of the structure, lm is the length of the scour downstream of the structure, l*m is the length of the scour at the end of the top-part of the structure, z'm is the maximum height of the ridge, l'm is the ridge length, l is the entire length of the structure, xm is the location of the maximum scour and w is the maximum development of the scour hole width. The test ranges are shown in Table 3. The densimetric particle Froude number is Fd = Q’/{l·hst[g(Gs-1)d50]

0.5} where Q’ is the effective flow discharge, Gs= ρs /ρ, in which ρs = bed material density and ρ = water density, d50 is the mean particle diameter and g = gravitational acceleration. Sand as bed material was used for the channel whose Gs = 2.60 and d50 = 1.60 mm. At the beginning of each experiment, the channel bed was carefully leveled. The effective flow discharge was calculate based on ratio b/B, so Q’=(b/B)Q where Q is the total channel flow discharge. Two series of experiments were carried out. The first series included tests on J-Hook structure in horizontal channel bed with b/B = 0.6 for different values of the height of the structure, discharge, Δy and the opening ratio ε=nδ/l2, in which n is the number of the top-openings. The second series of experiments included the same hydraulic conditions of the first series of experiments for J-Hook structure with b/B = 0.5. All the experiments were conducted for structure with α = 20°. Fig. 24 demonstrates the scour hole and ridge formation in J-Hook vane during the test run.

Fig. 22 Schematic diagram of the experimental channel setup II

35

Fig. 23 plan, two streamwise views A-A, C-C and a cross section D-D of J-Hook

Fig. 24 J-Hook vane during test run

36

Table 3 J-Hook Vane data test range

Test No. Q (m3/s) b/B ε ∆y (m) hst (m) Fd zm (m) z*m (m)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

0.0051 0.0102 0.0201 0.0093 0.0052 0.0071 0.0103 0.0151 0.0052 0.0053 0.0101 0.0501 0.0051 0.0252 0.0502 0.0151 0.0153 0.0251 0.0502 0.0151 0.0152 0.0151 0.0503 0.0251 0.0152 0.0151 0.0501 0.0251 0.0152 0.0153 0.0501 0.0251 0.0152 0.0252 0.0503 0.0051 0.0251 0.0102 0.0051 0.0101 0.0251 0.0052 0.0101 0.0251 0.0052 0.0102 0.0251 0.0052

0.7 0.7 0.7 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.5 0.5 0.5 0.5 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

0.205 0.205 0.205 0.167 0.167 0.167 0.083 0.083 0.083 0.333 0.333 0.333 0.333 0.333 0.333 0.333 0.167 0.167 0.167 0.625 0.331 0.331 0.331 0.331 0.333 0.333 0.169 0.169 0.169 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.500 0.169 0.169 0.169 0.338 0.338 0.338 0.500 0.500 0.500 0.338

0.007 0.006 0.005 0.007 0.007 0.008 0.006 0.006 0.007 0.007 0.009 0.005 0.007 0.010 0.005 0.010 0.010 0.014 0.004 0.010 0.009 0.010 0.003 0.010 0.008 0.011 0.002 0.008 0.010 0.008 0.001 0.007 0.007 0.009 0.002 0.004 0.005 0.005 0.006 0.010 0.011 0.006 0.010 0.012 0.004 0.005 0.001 0.001

0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.062 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.041 0.021

0.639 1.277 2.555 1.106 0.615 0.860 1.229 1.844 0.615 0.615 1.229 6.146 0.410 2.049 4.098 1.229 1.229 2.049 4.098 1.229 1.143 1.143 3.811 1.905 1.229 1.052 3.811 1.905 1.143 1.143 3.811 1.905 1.229 2.049 4.098 0.615 3.073 1.229 0.572 1.143 2.858 0.572 1.143 2.858 0.572 1.143 2.858 1.143

0.024 0.056 0.054 0.050 0.030 0.041 0.031 0.042 0.022 0.028 0.053 0.066 0.027 0.062 0.062 0.050 0.048 0.060 0.054 0.081 0.062 0.056 0.049 0.046 0.058 0.069 0.061 0.063 0.056 0.053 0.036 0.068 0.077 0.046 0.044 0.029 0.035 0.048 0.033 0.036 0.050 0.027 0.053 0.060 0.038 0.054 0.032 0.000

0.032 0.060 0.051 0.042 0.033 0.044 0.046 0.074 0.049 0.036 0.052 0.098 0.037 0.085 0.079 0.054 0.060 0.092 0.073 0.087 0.083 0.060 0.091 0.070 0.083 0.072 0.095 0.115 0.086 0.064 0.083 0.112 0.069 0.079 0.073 0.024 0.051 0.053 0.050 0.057 0.084 0.041 0.056 0.114 0.038 0.053 0.044 0.000

37

Table 3 J-Hook Vane data test range (continue)

Test No. Q (m3/s) b/B ε ∆y (m) hst (m) Fd zm (m) z*m (m)

49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67

0.0101 0.0501 0.0252 0.0151 0.0102 0.0151 0.0251 0.0101 0.0152 0.0252 0.0251 0.0352 0.0502 0.0251 0.0352 0.0501 0.0252 0.0351 0.0503

0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6

0.338 0.338 0.338 0.338 0.169 0.169 0.169 0.500 0.500 0.500 0.167 0.167 0.167 0.333 0.333 0.333 0.500 0.500 0.500

0.001 0.001 0.001 0.004 0.005 0.006 0.001 0.003 0.006 0.003 0.018 0.026 0.006 0.016 0.010 0.006 0.014 0.009 0.010

0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.021 0.092 0.092 0.092 0.092 0.092 0.092 0.092 0.092 0.092

2.286 11.432 5.716 3.429 2.286 3.429 5.716 2.286 3.429 5.716 1.366 1.912 2.732 1.366 1.912 2.732 1.366 1.912 2.732

0.027 0.036 0.031 0.034 0.021 0.043 0.030 0.024 0.038 0.040 0.081 0.077 0.064 0.057 0.064 0.063 0.074 0.062 0.080

0.027 0.054 0.029 0.042 0.027 0.046 0.047 0.034 0.042 0.049 0.170 0.141 0.100 0.157 0.097 0.102 0.139 0.089 0.105

Following graph shows the granulometry curve of the sand which is uniform sand with particle uniformity factor σ = (d84/d16)

0.5 = 1.26.

Fig. 25 Granulometry of the bed material

38

2.1.3. Setup III

The same channel setup and instrumentation of J-Hook vane experiments has been used to study the scour downstream of W-weir in-stream structures. Fig. 26 shows a plan, a stream wise view A-A and two cross sections C-C and D-D of the channel with the main parameters of the flow and the scour. In Fig. 26 α1 and α2 are the outer and inner arm angles of the structure respectively in respect to the river bank, l1 and l2 are the lengths of the outer arm and inner arm of the structure, y0 is the approach flow depth, hst is the height of the structure (defined as the average height of the stones top) and to avoid the scale effect 3 different heights of structures were made using stones in average top heights of 31, 62 and 92 mm. Δy is the difference between water surface upstream and downstream of the structure at the maximum scour depth, δ is the width of each top-opening of the structure, B is the channel width, zm is the maximum depth of the scour downstream of the W-weir, , lm is the length of the scour downstream of the structure, z'm is the maximum height of the ridge, l'm is the ridge length, l is the entire length of the structure, xm is the location of the maximum scour and w is the maximum development of the scour hole width. The densimetric particle Froude number is Fd = Q/{l·hst[g(Gs-1)d50]

0.5} where Q is the effective flow discharge, Gs= ρs /ρ, in which ρs = bed material density and ρ = water density, d50 is the mean particle diameter and g = gravitational acceleration. Uniform sand with particle uniformity factor σ = 1.26 as bed material was used for the channel whose Gs = 2.60 and d50 = 1.60 mm. At the beginning of each experiment, the channel bed was carefully leveled. To avoid scour and dune deformation the submersible pump was used to suck the water while the downstream gate was closed.

Fig. 26 Plan view and cross sections of a) W-weir b) W-weir with openings

tw

tw y0

y0 tw

tw y0

y0

(b) (a)

39

Two series of experiments were carried out. The first series includes the experiments on W-weir without opening and the second series contains the tests on W-weir with openings. In order to have different l/B, two values of α have been used as outer and inner arm angle of W-weir structure. α1 = α2=20° then l/B=2.7, α1 =20° and α2=30° then l/B=2, α1

= α2=30° then l/B=1.7. Fig. 27 depicts an upstream view of the W-weir structure before the test run.

Fig. 27 an upstream view of the W-weir structure before the test run

40

2. 2. Instrumentation

2.2.1 Point Gauge

The clear water flow depth and bed profile were measured using a point gauge of 0.1 mm precise (Fig. ). The point gauge was placed on a moving trolley which can move upstream and downstream to measure different sections in the channel. The gauge readings were taken when 50% time the point gauge tip touches the water surface.

Fig. 28 point gauge and in inset the vernier showing 0.1 mm precise

2.2.2 Ultrasonic distance measuring sensors

At the end of each experiment the morphology of scour and dune has been surveyed using “Ultrasonic Baumer” which has scanning range of 60 – 400 mm (Fig. 29). The minimum distance to place the sensor is 60 mm above the bed but to escape all problems of of hollow cone, it was placed at 200 mm above the reference bed.The precision of the sensor is 0.5 mm based on the catalogue but it has been considered that 1 mm is more practical. Figure 30 compares the measurements using point gage and ultrasonic sensor with perfect agreement line in mm.

Fig.29 Ultrasonic Baumer

41

Fig. 30 compaison of the manual measurements versus ultrasonic sensor

2.2.3 Magnetostrictive Linear Position Transducer (GEFRAN) To find the longitudinal position along with using “Ultrasonic Baumer”, the

“GEFRAN” has been used. Therefore each lomgitudinal passage of ultrasonic sensor leads to one longitudinal survey in one y of channel width. each 5 cm of the width of the channel was surveyed at the end of each experiment. GEFRAN has been shown in Fig. 31.

Fig. 31 Magnetostrictive Linear Position Transducer (GEFRAN)

42

3. DIMENSIONAL ANALYSIS

Before starting to analyze the data obtained from the experiments and discussion on the results, it is necessary to define the dimensionless parameters, through the using of the theorem of Buckingham and Incomplete Self-Similarity cited by Barenblatt (1987).

The main parameters to determine the maximum scour depth are:

0),,,,,,,,,,,( 050 ShdgQyBlhzf twsstm (1)

According to the theorem of Buckingham, it can be said that the same phenomenon can be described as a function of dimensionless parameters of n-x, meaning n as the number of dimensional parameters of the original function and x as the number of basic dimensions (or primary quantities) present in these parameters. In this specific case, we have:

n = 12

x =3 which includes mass (M), length (L) and time (T)

Therfore: nπ = n – x = 9

First, the nine dimensionless parameters that govern the phenomenon have been chosen based on the main objective of this thesis, which is to predict the maximum scour depth. The scour depth has been normalized by dividing by the height of the structure:

st

m

h

z1

The next eight dimensionless parameters were obtained using equation systems with 3 equations and 3 variables, as it is described below:

gdQ cba 222502

2313000 222 LTLMLTLTLM cba

2

550

2

2

2

2

2

2

222

52

0

002

0133

Q

gd

cab

ba

cba

ydQ cba 333503

LLMLTLTLM cba 333 313000

503

3

3

3

3

3

333

100

00

0133

d

y

cab

ba

cba

43

Similarly:

504

d

hst

505

d

B

506

d

l

507

d

htw

while:

scba dQ 888

508

3313000 888 MLLMLTLTLM cba

s

cba

ba

cba

8

8

8

8

8

8

888

01

0

010

0333

π9 = S0

At this point it is possible to consider the phenomenon as described by the relation:

0),,,,,,,,( 987654321 f (2)

Whereas the purpose is the prediction of the depth of scour, therefore:

),,,,,,,( 987654321 f (3)

And that is:

0

50505050502

550 ,,,,,,, S

d

h

d

l

d

B

d

h

d

y

Q

gdf

h

z stwst

st

m

(4)

To further simplify the dimensionless equation describing the phenomenon, the Incomplete

Self-Similarity thecnique (Barenblatt 1987) has been used. Practically, by combining all the

π parameters, it was possible to reduce the number of parameters to 4. In fact:

4

7

5

6

4

3

26

2472

01 ,,,11

1

11)1(

cbSa (5)

In case of horizontal channel bed (S0=0), (1± S0b) c=1.

44

Where:

2

26

2472

11

1

11dF

sth

y

4

3

B

l

5

6

st

tw

h

h

4

7

By substituting parameters:

st

tw

std

cb

st

m

h

h

B

l

h

yFSa

h

z,,,)1( 2

0 (6)

Based on dimensional analysis and incomplete self-similarity (Barenblatt 1987) Eq. (6) can

be shown in a power-law expression as follow:

std

e

st

twd

cb

st

m

h

yF

h

h

B

lSa

h

z,)1( 0 (7)

where a, b, c and d are constants to be obtained experimentally, while Fd is the particle densimetric Froude number, depending on the flow characteristics, the structure geometry and the bed material.

This analytical expression Eq. (7) determines the maximum depth of scour for different hydraulic conditions and geometry of the structure. With the substitution of the variables in the process of dimensional analysis, the equations can also be found in order to determine the other scour parameters.

D’Agostino and Ferro (2004) presented a non-dimensional group related to d50 as A50 = Q/{B·z[g((ρs-ρ)/ρ)d50]

0.5} where B is the width of channel and z is the height of the weir to take into account more the effect of the sill geometry. Scourlock et al. (2012) defined F*= Q/{b·z[g(Δ-1)d50]

0.5} as densimetric particle Froude number where b is the length of the structure and z is the height of the structure and Δ=(ρs/ρ). In the current study also Fd = Q/{l·hst[g(Gs-1)d50]

0.5} has been defined as densimetric particle Froude number for in-stream grade-control structures where l is the length of the structure and hst is the height of the structure and in compare with the classic densimeric Froude number, instead of approach flow velocity the jet velocity is influenced by the geometry of the structure.

Experimental data leads to define η = Fd2·Δy/hst as non-dimensional scour parameter

and considering f=constant, Eq. (7) can be expressed mathematically as follows:

fe

st

twd

cb

st

m

h

h

B

lSa

h

z

)1( 0 (8)

45

4. EXPERIMENTAL RESULTS AND DISCUSSIONS

This chapter includes experimental results of scour properties downstream of eco-friendly in-stream structures in different flow conditions. This chapter gives detail information and comparison on the evaluation of the main scour parameters and scour typology for three different grade-control structures.

4. 1 Scour typology

Experimental data show that the scour type varies with the scour parameter which can be defined as a non-dimensional number η = Fd

2·Δy/hst. The experimental results show that this parameter works well to classify the scour morphology downstream of in-stream grade-control structures.

4. 2.1 Cross-Vane Scour typology

Three types of scour have been defined based on experimental results. Type 1: long scour-long ridge, Type 2: short scour-long ridge and Type 3: short scour-short ridge. Fig. 2 shows these three scour types in U-shape structure. In this figure vertical and horizontal axes are measured in centimeters and are representing the distance in width and along the channel respectively. Fig. 32(a) illustrates scour Type 1 for U-shape structure with l/B = 2.3, Fd = 1.28, Δy/hst = 0.125 on horizontal channel bed. The elevation of 32 cm is the initial channel bed level. It indicates if lm /B and l’m /B are both greater than 2.5 then a long scour-long ridge is formed. Fig. 32(b) represents scour Type 2 for U-shape structure with l/B = 2.3, Fd = 0.96, Δy/hst = 0.15 and S0 = 0. It is clear that the lm /B is smaller than 2 but l’m /B is greater than 2.5 then a short scour-long ridge occurs. Finally Fig. 32(c) shows scour Type 3 for U-shape structure with l/B = 1.7, Fd = 1.17, Δy/hst = 0.2 on horizontal channel bed. As it appears both the lm /B and l’m /B are smaller than 2 then a short scour-short ridge is present. This is very important that in all three parts of Fig. 32, the scour is almost symmetric and it shows that in U-shape structure the effect of the weir crest shape is the minimum and scour concentrates in the center line of the channel. Based on this definition all the experimental results are reported in Fig. 33. It shows by increasing η the type of scour changes from short to long scour. Fig. 33(a) indicates the scour typology for I-shape structure with l/B = 1 on horizontal bed. Fig. 33(b) shows variation of types of scour for U-shape structure with l/B = 1.7, S0 = 0 and Fig. 33(c) shows the scour typology for U-shape structure with l/B = 2.3, S0 = 0. The no-scour zone reduces by increasing the l/B. Fig. 33(d-f) illustrates scour formation for U-shape structure with l/B = 2.3 for different bed slopes (d) S0 = 0.01; (e) S0 = 0.025; and (f) S0 = 0.05. It proves that, practically, increasing the channel bed slope only increases the Δy/hst and does not affect the scour typology and always by increasing η the scour type changes from Type 3 to Type 2 and finally to Type 1. The hatched lines represent uncertainty regions in passing from one scour type to another one. Comparison of the ridge centerline profiles with the scour typology indicates that three types of scour have significant ridge profile forms which are shown in Fig. 34. In scour type 3 the location of the maximum ridge height is placed close to the weir while for scour type 2 it is in the middle of the ridge profile and in scour type 1 is close to the end of the ridge profile.

46

Fig. 32 Scour types (a) Type 1 for U-shape structure with l/B = 2.3, Fd = 1.28, Δy/hst = 0.125 and S0 = 0. Elevation 32 is the initial channel bed level; (b) Type 2 for U-shape structure with l/B = 2.3, Fd = 0.96, Δy/hst = 0.15 and S0 = 0; (c) Type 3 for U-shape structure with l/B = 1.7, Fd = 1.17, Δy/hst = 0.2 and S0 = 0.

47

Fig.33 (a) scour typology for I-shape structure with l/B = 1 and, S0 = 0; (b) variation of types of scour for U-shape structure with l/B = 1.7, S0 = 0; (c) scour typology for U-shape structure with l/B = 2.3, S0 = 0; (d-f) scour formation for U-shape structure with l/B = 2.3 for different bed slopes (d) S0 = 0.01; (e) S0 = 0.025; and (f) S0 = 0.05.

Fig. 34 Comparison of the ridge profiles for different scour types.

48

4. 3.2 J-Hook Vane Scour typology

The same as Cross-Vane structures, for J-Hook Vane also based on experimental results three types of morphologies could be defined. Type 1: long scour-long ridge, Type 2: short scour-long ridge and Type 3: short scour-short ridge. Fig. 3 shows these three scour formations. In this figure vertical and horizontal axes are measured in millimeters and are representing the distance in width and along the channel respectively. Fig. 35(a) illustrates scour Type 1 for J-Hook structure with b/B = 0.6, Fd = 2.05, Δy/hst = 0.233 on horizontal channel bed. The elevation of 308 mm is the initial channel bed level. It indicates, if lm /B and l’m /B are both greater than 1, that a long scour-long ridge is formed. Fig. 35(b) represents scour Type 2 for J-Hook structure with b/B = 0.6, Fd = 1.23, Δy/hst = 0.17 on horizontal channel bed. It is clear that the lm /B is smaller than 1, but l’m /B is greater than 1, then a short scour-long ridge occurs. Finally Fig. 35(c) shows scour Type 3 for J-Hook structure with b/B = 0.5, Fd = 1.14, Δy/hst = 0.13 on horizontal channel bed. As it appears both the lm /B and l’m /B are smaller than 1 then a short scour-short ridge is present. Fig. 35(c) depicts that the effect of the J-Hook structure as a spur in b/B = 0.5 if compared with structures in Fig. 35(a, b) with b/B = 0.6 is less and practically there is just one scour hole downstream of the structure contrariwise Fig. 35(a, b) shows J-Hook vane with b/B = 0.6 in which very long scour occurs at the right bank of the channel. Based on this definition all the experimental results are reported in Fig. 36. It shows by increasing η the type of scour downstream of the structure changes from short to long scour. It means that practically by increasing the densimetric Froude number, the scour type changes from Type 3 to Type 2 and finally to Type 1. The hatched lines represent uncertainty regions in passing from one scour type to another one.

49

Fig.35 (a) scour Type 1 for J-Hook structure with b/B = 0.6, Fd = 2.05, Δy/hst = 0.233 on

horizontal channel bed; (b) scour Type 2 for J-Hook structure with b/B = 0.6, Fd = 1.23,

Δy/hst = 0.17 on horizontal channel bed; (c) scour Type 3 for J-Hook structure with b/B =

0.5, Fd = 1.14, Δy/hst = 0.13 on horizontal channel bed. The reference bed level is 308 mm.

50

Fig. 36 Scour typology for J-Hook vane

4. 4.3 W-wier Scour Typology

The scour morphology downstream of W-weirs is different respect to Cross-Vane and J-Hook vane structures. In the sence that many times there are more than one scour hole and one ridge. Based on experimental data the scour morphology downstream of the W-weirs also can be classified with the non-dimensional scour parameter η = Fd

2·Δy/hst. Three types of morphologies have been defined based on experimental results. Type A: one scour hole-two ridges, Type B: two scour holes-two ridges and Type C: one scour hole-one ridge which are shown in Fig. 37. In this figure vertical and horizontal axes are measured in millimeters and are representing the distance in width and along the channel respectively. Fig. 37(a) illustrates scour Type A for W-weir with l/B = 2.55, Fd = 0.338, Δy/hst = 0.667 and η = 0.076 on horizontal channel bed. The elevation of 0 mm is the initial channel bed level. Fig. 37(b) represents scour Type B for W-weir with b/B = 2.55, Fd = 0.513, Δy/hst = 0.398 and η = 0.105 on horizontal channel bed. Finally Fig. 37(c) shows scour Type C for W-weir with b/B = 2.55, Fd = 1.095, Δy/hst = 0.147 and η =0.177 on horizontal channel bed. The scour and dune formation during the test run has been shown in Fig. 38.

4. 5.4 Conclusion

Comparison of scour morphologies ocoured downstream of studied in-stream structures indicates that practically in all studied in-stream structures η and l/B are important to classify the scour formation. Cross-Vane and J-Hook vane always have dune in the line of scour hole and can be classified as long scour-long ridge, short scour-long ridge and short scour-short ridge. But in W-weir because of precence of two vanes the scour morphology forms in different way. It can be categorized as one scour hole-two ridge, two scour hole-two ridge and one scour hole-one ridge.

51

Fig. 37(a) illustrates scour Type A for W-weir with l/B = 2.55, Fd = 0.338, Δy/hst = 0.667 and η = 0.076 on horizontal channel bed. The elevation of 0 mm is the initial channel bed level (b) represents scour Type 2 for W-weir with b/B = 2.55, Fd = 0.513, Δy/hst = 0.398 and η = 0.105 on horizontal channel bed. Finally and (c) shows scour Type C for W-weir with b/B = 2.55, Fd = 1.095, Δy/hst = 0.147 and η =0.177 on horizontal channel bed.

Fig. 38 Scour and dune formation during test run for W-weir

52

4.2 Maximum Scour Depth

Based on dimensional analysis explained in chapter 2 and experimental data the maximum scour depth downstream of Cross-Vane structures can be expressed by Eq. (9) which is the mathematical form of Eq. (7). The ratio htw/hst was around one for all experiments.

4.0

9.0

9.01.00 )1(3.1

B

lS

h

z

st

m 0.05 < η < 15 (9)

Fig. 39 shows all the 86 tests data from Table 1 and two sets of data from Scurlock et al. (2012). The data are presented in a semi logarithmic scale. It shows that zm /hst is a function of η and it increases with increasing of l/B and S0. It shows that Eq. (9) for different values of S0 and l/B fit well on experimental data. In the Scurlock et al. (2012) data sets, the S0 varies from 0.0021 to 0.0047 and l/B varies from 1.3 to 3. The comparison of observed scour depths versus calculated zm /hst by Eq. (9) for current experimental data is shown in Fig. 40. It shows that all data are in ±20% deviation of perfect agreement line. As the channel bed slopes in all Scurlock et al. (2012) data are smaller than 0.5%, the assumption of horizontal channel bed results well-fitting the data with Eq. (9).

Fig.39 Comparison of Eq. (9) for various values of S0 and l/B with collected data and Scurlock et al. (2012) data; [−··−··−] l/B = 2.3 & S0 = 0.05, [---------] l/B = 2.3 & S0 = 0, [───] l/B = 1.3 & S0 = 0.0021 and [−−−−] l/B = 1 & S0 = 0.

Fig.40 Comparison of observed scour depths versus calculated zm /hst by Eq. (9) for current experimental study data.

53

Eq. (10) which has been shown in Fig. 41 is the mathematical form of Eq. (7) to predict the maximum scour downstream of J-Hook vane structures. The observed data shows that δ (opening) is not effective on the main scour geometry parameters and the scour morphology downstream of J-Hook vane can be estimated by . As all the experiments have been done on unique J-Hook vane structure with l/B around 1 on horizontal bed channel, then Eq. (8) can be expressed as follows:

2.04.1 st

m

h

z 0.01 < < 4 (10)

Fig. 41 shows the experimental observations. The data are presented in a semi

logarithmic scale. It indicates that zm /hst can be simply predictable using Eq. (10) has correlation coefficient of 0.74. The comparison of observed scour depths versus calculated zm /hst by Eq. (10) for current experimental data and also Scurlock et al. (2012) data for U-shape and W-shape cross-vane are shown in Fig. 42. It shows that all data are in ±30% deviation of perfect agreement line. U-shape cross-vane is the closest structure to the J-Hook vane among the grade-control structures presented in literature.

Fig.41 Comparison of Eq. (10) with observed data

Fig.42 Comparison of observed scour depths versus calculated zm /hst by Eq. (10) for current experimental study data and Scurlock et al. 2012 data

54

The experimental data of W-weir classified by l/B and htw/hst are shown in Fig. 43. As it appears both l/B and htw/hst are effective on maximum scour depth. The plan view and upstream view of scour and dune formation downstream of the W-weir are shown in Fig. 44 and Fig. 45.

Fig.44 Plan view of the scour and dune formation downstream of W-weir

Fig.43 W-weir data classified by l/B and htw/hst

Fig.45 Upstream view of the scour and dune formation downstream of W-weir

55

4.3 Maximum Scour Lentgh

Another important design feature is the length of the scour hole. Based on the same logic of dimensional analysis for the maximum scour depth, substituting the lm instead of zm, Eq. (7) can be shown as follows:

std

e

st

twd

cb

st

m

h

yF

h

h

B

lSa

h

l,')1('

''

''0 (11)

Where a’, b’, c’, d’ and e’ are constants to be assessed from experimental data and Φ’=

functional symbol. As for all experiments htw/hst=1 therefore experimental observations on Cross-Vane structure result Eq. (12) which is the numerical form of Eq. (11) to determine the maximum scour length for different l/B and S0.

6.0

9.1

9.14.00 )1(8.8

B

lS

h

l

st

m 0.05 < η < 15 (12)

Fig. 46 shows Eq. (12) for different values of S0 and l/B which lines fit well on experimental data. It shows that increasing l/B increases the scour length but increasing the channel bed slope decreases the length of the scour. The comparison of observed scour lengths versus calculated lm /hst by Eq. (12) is shown in Fig. 47. It shows that the major parts of data are in ±30% deviation of perfect agreement line.

Fig.46 Comparison of Eq. (12) for various values of S0 and l/B with collected data; [−··−··−] l/B = 2.3 & S0 = 0, [───] l/B = 2.3 & S0 = 0.025, [------] l/B = 1.7 & S0 = 0, [― ― ―] l/B = 2.3 & S0 = 0.05 and [········]

56

Experimental observations on J-Hook vane structure result Eq. (13) with correlation coefficient of 0.80, to determine the maximum scour length downstream of J-Hook vane in horizontal channel. The data indicates that the effect of tail water is negligible and as all the experiments on J-Hook vane have been carried out for l/B=1 then the phenomenon can be expressed by a simple equation as follows:

5.08.23 st

m

h

l 0.01 < η < 4 (13)

All the experimental data and Eq. (13) are shown in Fig. 48. Figure 49 indicates that major parts of the data are in 30 percent of deviation of perfect agreement line.

Fig.47 Comparison of observed maximum scour lengths versus calculated lm /hst by Eq. (12) for current experimental study data l/B = 1 & S0 = 0.

lm

/hst

Fig.48 Comparison Observed maximum scour lengths data for J-Hook vane for l/B=1 & S0=0 with Eq. (13).

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W-weir experimental data show that l/B also is important to study the maximum scour length parameter. Fig. 50 shows that increasing l/B increases the lentgth of the scour hole.

4.4 Maximum Scour Width

The scour width is a parameter which is very dependent on the scour morphology. As it was mentioned befor, in W-weir the scour hole numbers varies with hydraulic condition and two separate scour holes and unique scour hope is probable. Because of this reason evaluating one equation to predict the maximum scour hole for W-weir was impossible. But for Cross-Vane and J-Hook vane the data leads to derive equations to estimate the maximum scour width.

Fig.49 Comparison of observed scour length versus calculated lm /hst by Eq. (13)

Fig.50 Classification of observed scour length data by l /B

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The observed data show that the scour hole width develops as wide as channel width in the I-Shape structure for all the tested channel bed slopes. Also in the U-Shape structure for S0 =1, 2.5 and 5% the scour hole’s width is equal to the width of the channel in the experimental data range. The U-Shape structure in horizontal channel bed controls the width of the scour hole. Fig. 51 shows that the width of the scour hole is independent of l/B and can be explained by Eq. (14) with a correlation coefficient of 0.73. w /B = 0.95 0 < < 1 (14)

As it appears increasing increases the width of the scour hole in horizontal channel bed.

The observed data show that the scour hole width, mostly develops from 0.7 to 0.9

channel width in the J-Hook structure for all the hydraulic conditions. Fig. 52 shows that the width of the scour hole can be explained by Eq. (15) with a correlation coefficient of 0.60.

w/B = 0.8 0.01 < < 4 (15) As it appears, increasing η increases the width of the scour hole in horizontal channel bed.

Fig.51 Comparison of Eq. (14) for various values of l/B with collected Cross-Vane data in the horizontal channel bed condition.

Fig.52 Comparison of Eq. (15) with collected J-Hook vane data in the horizontal channel bed condition.

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4.5 Maximum Scour Location

Investigation on collected data shows that l/B is the most important effective parameter on longitudinal scour formation. Fig. 53 shows that by increasing l/B the maximum scour location of the channel moves toward the weir, in which z is the bed level in each x of the scour length. The observations show that xm/lm also is a function of η. Fig. 54 shows that xm/lm is independent from the channel bed slope and data well fit with the following equation to determine the location of the maximum scour depth. xm /lm = 0.4(l/B)-2η . 0.05 < η < 15 (16)

As it appears Eq. (16) is a function of scour parameter η and l/B is the coefficient which changes the slope of the curves. Fig. 54 shows that by increasing l/B the parameter xm /lm decreases; it means that the location of the maximum scour depth is closer to the structure. The observed xm /lm versus calculated values have been compared in Fig. 55. It indicates that all data are in ±30% deviation of perfect agreement. Fig. 56 shows the scour side view downstream of I-shape structure during the test run.

Fig.53 Longitudinal scour profile patterns of the channel for different l/B.

Fig.54 Comparison of Eq. (16) for various values of l/B with collected data (independent of S0); [−··−··−] l/B = 1, [───] l/B = 1.7, [------] l/B = 2.3.

Fig.55 Comparison of observed locations of the scour depths versus calculated xm /hst by Eq. (16) for current experimental study data.

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Studying on collected data on J-Hook vane shows that approach Froude number Fr is

the effective parameter on longitudinal scour formation. Fig. 57 shows that by decreasing Fr, the maximum scour location of the channel moves toward the structure, in which z is the bed level in each x of the scour length.

4.6 Maximum Ridge Heigth and Length

As it explained before, downstream of a J-Hook vane structure there is just one unique ridge which has the same trend of scour data and it results Eq. (17) to determine the maximum ridge height for J-Hook vane in horizontal channel.

z'm /hst = 0.6η0.3 0.01 < η< 4 (17) Fig. 58 shows Eq. (17) which fits well on experimental data with correlation

coefficient of 0.62. Investigation on ridge length data clarifies that as well as the other scour geometry

parameters, η is the variable which ridge length depends on. Eq. (18) illustrates the phenomenon.

l'm /hst = 31.9η0.6 0.01 < η< 4 (18)

Fig.56 Scour side view downstream of the I-shape structure.

Fig.57 Non-dimensional longitudinal scour profiles for different approach Froude numbers.

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Fig. 59 depicts Eq. (18) which fits well on experimental data with correlation coefficient of 0.86.

4.7 Detail Study on W-weir with Top-Openings

W-weir is an in-stream grade-control structure which has defined in literature as a closed structure. In this part of study W-weir with top-openings δ=10% and 20% were modeled to know which is the important effect if there is W-weir with top-openings. Observations data show that the top-openings are effecting on maximum scour depth and the location which the maximum scour depth occurs. The detail explanations of these effects are presented as follows:

Fig.59 Comparison of Eq. (18) with observed length of the dune for J-Hook Vane;

Fig.58 Comparison of Eq. (17) with observed heigth of the dune for J-Hook Vane;

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3.7.1 Effect of Top-Openings on Maximum Scour Depth

To understand the phenomenon one non-dimensional parameter δ/B has been defined which δ is the sum of top-openings of the structure and B is the channel width. The ratio δ/B=0 is related to the complete closed W-weir (2.5 < l/B< 3). In this series of experiments, the same tests which have been done for complete closed W-weir have been repeated with W-weir which there was top-openings. Two openings 10 and 20 percents were chosen. The experimental data showed that the results of experiments with 10% of opening and 20% of opening are much closed then to show better the effect of top-opening, it can be presented as a unique data series. (Fig. 60)

3.7.2 Effect of Top-Openings on Maximum Scour Location

As it was explained before downstream of open W-wier less scour occur and it appears in two dimensional longitudinal profiles presented in Fig. 61 and fig. 62. As it has been shown in these figures also the location of maximum scour has been displaced.

Fig.60 Classification of observed scour depth data downstream of open W-weir by δ /B

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Fig.61 Comparison of dimensional longitudinal profiles for closed W-weir and open W-weir for Q=25 l/s

Fig.62 Comparison of dimensional longitudinal profiles for closed W-weir and open W-weir for Q=10 l/s

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CONCLUSION

Two types of Cross-Vane structures, I-shape and U-shape, were studied to investigate the scour morphology downstream of eco-friendly In-stream structures. Dimensional analysis resulted in a new analytical function predicting the maximum scour depth for different combinations of hydraulic conditions, riverbed slopes and structures geometry. A new dimensionless parameter η showed that densimetric Froude number, drop height and height of the structure are the main scour parameters to predict the maximum scour depth, the maximum scour length, the location of the maximum scour depth and the maximum development of scour hole width and classifying the scour type. Results show, that a classification of scour type can be done as a function of the non-dimensional parameters l/B and η. The maximum scour depth position in the longitudinal scour profile depends on l/B and is independent of S0. By increasing l/B the maximum scour depth position moves toward the structure. I-Shape structure in all channel bed slopes is not able to control the scour hole width and it is as wide as the channel width. U-Shape structure in horizontal channel bed can control the width of the scour hole and for S0 >1 the width of the scour hole is the same as the channel width. Scour typology included three types of scour. Type 1: long scour-long ridge which lm /B and l’m /B are both greater than 2.5 and the maximum ridge height is placed close to the end of the ridge profile. Type 2: short scour-long ridge, it means lm /B is smaller than 2 but l’m /B is greater than 2.5 and the maximum ridge height is in the middle of the ridge profile and Type 3: short scour-short ridge which both the lm /B and l’m /B are smaller than 2 and the location of the maximum ridge height is placed close to the weir. Increasing η changes the scour type from Type 3 to 2 and finally to Type 1.

Two series of experiments on J-Hook-Vane structure were carried out to investigate the scour morphology downstream of this type of eco-friendly in-stream structure. Incomplete self-similarity and dimensional analysis resulted in an analytical function predicting the maximum scour depth for different combinations of hydraulic conditions and structure geometries. Dimensionless parameter η showed that densimetric Froude number, drop height and height of the structure are the main scour parameters to predict the maximum scour depth, the maximum scour length, maximum height and length of the ridge and the maximum development of scour hole width and classifying the scour type. The results show that increasing η all the scour geometry parameters increase. The maximum scour depth position in longitudinal scour profile depends on approach Froude number Fr. By decreasing Fr the maximum scour depth position moves toward the structure. The scour hole width varies from 0.7 to 0.9 of the channel width. Scour typology included three types of scour. Type 1: long scour-long ridge, Type 2: short scour-long ridge and Type 3: short scour-short. Increasing η changes the scour type from Type 3 to 2 and finally to Type 1.

Two type of W-weir have been studied. Closed W-weir and open W-weir were investigated to study the behaviors of this eco-friendly in-strem structure. Observation data show that the maximum scour depth is influenced by l/B and htw/hst and increasing the htw/hst decreases the scour depth. Also increasing δ/B which is the effect of top-openings in open W-weir decreases the scour depth. The maximum scour length downstream of W-weir is dependent only to l/B and η and is independent of htw/hst. The location of maximum scour depth for large values of l/B>2.5 is independent of tail water depth but for l/B<2.2 depends to η and htw/hst. In open W-weir the location of maximum scour occurs at about xm=0.5 lm in which in complete closed W-weir the location of maximum scour occurs at about xm=0.2 lm and is close to the structure respect to the open W-weir. The maximum ridge height and length downstream of W-weir are function of l/B and η and are independent of teil water

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depth. Experimental data shows by increasing η the type of scour downstream of the W-weir changes from one scour hole-two ridge to two scour hole-two ridge and finally one scour hole-one ridge. It means that practically by increasing the densimetric Froude number, the scour type changes from Type C to Type B and finally to Type A. The hatched lines represent uncertainty regions in passing from one scour type to another one.

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REFERENCES

Bailey, P., and Fischenich, J.C. (2003). "Landscaping Considerations for Urban Stream Restoration.” EMRRP Technical Notes Collection. Document no. ERDC TN-EMRRP-SR-42, U.S. Army Corps of Engineers, Ecosystem Management and Restoration Research Program. Vicksburg, MS. p. 4.

Barenblatt, G. I. (1987).“Dimensional Analysis” Gordon and Breach Science Publishers, ISBN 3-7186-0438-8.

Bates, A. «Channel stabilization using constructed riffles.» Ecosystem Restoration Workshop, Kamloops, BC, Canada, 28 February, 2006.

Ben Meftah, M. and Mossa, M. «Scour Holes Downstream of Bed Sills in Low-Gradient Channels.» J. Hydr. Res., 2006: 44(4), 497-509.

Bernhardt PMA, Alexander AJD, Barnas GK, Brooks S, Carr J, Clayton S, Daham C, Follstad-Shah J, Galat D, Gloss S, Goodwin P, Hart D, Hassett B, Jenkinson R, Katz S, Kondolf GM, Lake PS, Lave R, Meyer JL, O’Donnell TK, Pagano L, Powell B, Sudduth E (2005) Synthesizing U.S. river restoration efforts. Science 308:636–637.

Bhuiyan, F., Hey, R. D. and Wormleaton, P. R. «Effects of Vanes and W-Weir on Sediment Transport in Meandering Channels.» Journal of Hydraulic Engineering, ASCE., 2009: 135 (5), 339-349.

Bhuiyan, F., Hey, R. D. and Wormleaton, P. R. (2007). “hydraulic Evaluation of W-Weir for River Restoration.” J. Hydraul. Eng., ASCE, 133(6), 596-609.

Bormann, N. E. and Julian, P. Y. (1991). “Scour Downstream of Grade-Control Structures.” J. Hydraul. Eng. ASCE,117(5), 579-594.

Brookes, Andrew (1996). Shields, F. Douglas. ed. River Channel Restoration: Guiding Principles for Sustainable Projects. John Wiley. ISBN 978-0-471-96139-0.

Brookes, Andrew (1989). Channelized Rivers: Perspectives for Environmental Management. John Wiley. ISBN 978-0-471-91979-7.

Cronin, Amanda (March-April 2003). "Restoring Paradise in Moscow, Idaho". Land and Water 47 (2): 18. ISSN 0192-9453.

D’Agostino, V., and Ferro, V. (2004). “Scour on alluvial bed downstream of grade-control structures.” J. Hydraul. Eng., 130(1), 24–37.

Dey, S., and R.V. Raikar (2007), Scour below a high vertical drop, J. Hydraul. Eng. ASCE, 133(5), 564-568.

Dey, S., and A. Sarkar (2006a), Scour downstream of an apron due to submerged horizontal jets, J. Hydraul. Eng. ASCE, 132(3), 246-257.

67

Dey, S., and A. Sarkar (2006b), Response of velocity and turbulence in submerged wall jets to abrupt changes from smooth to rough beds and its application to scour downstream of an apron, J. Fluid Mech. 556, 387-419.

Dey, S., and A. Sarkar (2008), Characteristics of submerged jets in evolving scour hole downstream of an apron, J. Eng. Mech. 134, 11, 927-936.

Dey, S., and B. Westrich (2003), Hydraulics of submerged jet subject to change in cohesive bed geometry, J. Hydraul. Eng. ASCE, 129(1), 44-53.

Farhoudi, J. and Smith, K.V.H. (1985). “Local scour profile downstream of hydraulic jump.” J. Hydraul. Res., 23(4), 343–358.

Federal Interagency Stream Restoration Working Group (United States)(2001). Stream Corridor Restoration: Principles, Processes, and Practices. GPO Item No. 0120-A; SuDocs No. A 57.6/2:EN 3/PT.653. ISBN 0-934213-59-3.

Gilman, Joshua B.; Karl, Jarrod (2009). "Challenges of Stream Restoration as a Stormwater Management Tool; Part 1: A designer's perspective". Stormwater 10 (3). ISSN 1531-0574. May 2009.

Gillilan, S., Boyd, K., Hoitsma, T. & Kauffman, M. (2005) Challenges in developing and implementing ecological standards for geomorphic river restoration projects: a practitioner’s response to Palmer et al. (2005). Journal of Applied Ecology, 42, 223–227.

Hager, W.H., and Oliveto, G. «Shields entrainment criterion in bridge hydraulics.» J. Hydraul. Eng., 2002: 128(5), 538-542.

Hassan, N. M. K. N., and Narayanan, R. (1985). “Local scour downstream of an apron.” J. Hydraul. Eng., 111(11), 1371–1385.

House, R. «An evaluation of stream restoration structures in a coastal Oregon stream 1981-1993.» North American Journal of Fisheries Management , 1996: 16, 272-281.

Hey, R. D. (1995). River Handbook II. Calow and Petts, eds., Blackwell, Oxford.

Jerry R. Miller R. Craig Kochel, " Assessment of channel dynamics, in-stream structures and post-project channel adjustments in North Carolina and its implications to effective stream restoration" Environ Earth Sci DOI 10.1007/s12665-009-0150-1 Springer-Verlag 2009.

Kondolf G. M. (2006). “River Restoration and Meanders.” Ecology and Society 11(2): 42.

Lagasse, P. F., Thompson, P. L., and Sabol, S. A. «Guarding against scour.» Civil Engineering, 1995: 65(6), 56-59.

Leopold, L.B., G.M. Wolman, and J.P. Miller. « Fluvial Processes in Geomorphology W.H. Freeman and Co. San Francisco.» 1964: 522pp.

68

Luther P. Aadland, Minnesota Department of Natural Resources, Division of Ecological Resources Stream Habitat Program, January 2010, "Reconnecting Rivers: Natural Channel Design in Dam Removals and Fish Passage".

Maryland Department of the Environment Water Management, 2000, Channel Stabilization and Rehabilitation Techniques, Maryland’s Guidelines To Waterway Construction.

Mason, P. J. and Arumugam, K. (1985). “Free Jet Scour Below Dams and Flipbuckets.” J. Hydraul. Eng., ASCE, 111(2), 220-235.

Mendocino County Resource Conservation District, Ukiah, CA (2008). "Robinson Creek Restoration Project." Project No. DWR P13-045.

Moerke, A. H., and G. A. Lamberti. «Restoring stream ecosystems: Lessons from a Midwestern state.» Restoration Ecology, 2004: 12(3), 327–334.

Montgomery County Department of Environmental Protection (MCDEP), Rockville, MD. "Benefits of Stream Restoration." 2010-04-13.

O'Neil, J., and L. Fitch. «Performance audit of in-stream habitat structures constructed during the period, 1982–1990, in southwestern Alberta.» Abstracts for American Fisheries Society Meeting, September 1992, Rapid City, South Dakota,, 1992: p. 4.

Pagliara, S. (2007). “Influence of Sediment Gradation on Scour Downstream of Block Ramps.” J. Hydraul. Eng., ASCE, 133(11), 1241-1248.

Pagliara, S., Kurdistani, S.M., Scour downstream of cross-vane structures, Journal of Hydro-environment Research (2013), http://dx.doi.org/10.1016/j.jher.2013.02.002

Pagliara, S., Mahmoudi Kurdistani, S., Scour downstream of J-Hook vane structures in straight rivers, Acta Geophysica (2013), under publishing.

Pagliara, S. and Palermo, M. (2008a). “Scour Control Downstream of Block Ramps.” J. Hydraul. Eng., ASCE, 134(9), 1376-1382.

Pagliara, S. and Palermo, M. (2008b). “Scour control and surface sediment distribution downstream of block ramps” Journal of Hydraulic Research Vol. 46, No. 3 (2008), pp. 334–343

Pagliara, S., Palermo M., and Carnacina, I. (2009). “Scour and hydraulic jump downstream of block ramps in expanding stilling basins” Journal of Hydraulic Research Vol. 47, No. 4 (2009), pp. 503–511

Pagliara, S. and Palermo, M. (2010). “Influence of Tailwater Depth and Pile Position on Scour Downstream of Block Ramps” Journal of Irrigation and Drainage Engineering, ASCE, 136(2), 120–130.

Pagliara, S., Palermo M., and Carnacina, I. (2011). “Expanding Pools Morphology in Live-Bed Conditions” Acta Geophysica, Vol. 59, No. 2, pp. 296-316.

69

Pagliara, S. and Palermo, M. (2011a). “Effect of Stilling Basin Geometry on Clear Water Scour Morphology Downstream of a Block Ramp” Journal of Irrigation and Drainage Engineering, ASCE, 137(9), 593–601.

Pagliara, S. and Palermo, M. (2011b). “ Block ramp failure mechanisms: criticai discharge estimation” Proceedings of the Institute of Civil Engineers - Water Management, Vol. 164, Issue WM6, Pages 303-309.

Pagliara, S., Palermo M., and Carnacina, I. (2012a). “Live-bed scour downstream of block ramps for low densimetric Froude numbers” International Journal of Sediment Research, Vol. 27(3), pp. 337–350.

Pagliara, S., Palermo, M. and Roy D. (2012b). “Stilling basin erosion due to vertical crossing jets” Journal of Hydraulic Research Vol. 50, No. 3, pp. 290–297.

Palmer, M.A., Bernhardt, E.S., Allan, J.D., Lake, P.S., Alexander, G., Brooks, S., Carr, J., Clayton, S., Dahm, C., Follstad Shah, J., Galat, D.J., Gloss, S., Goodwin, P., Hart, D.H., Hassett, B., Jenkinson, R., Kondolf, G.M., Lave, R., Meyer, J.L., O’Donnell, T.K., Pagano, L., Srivastava, P. & Sudduth, E. (2005) Standards for ecologically successful river restoration. Journal of Applied Ecology, 42, 208–217.

Puckett P, Jennings G (2007) Rock cross vane design. USDACSREES National Water Conference, January 28, 2007. USDA.

Radspinner, R. R., P. Diplas, Anne F. Lightbody, F. Sotiropoulos. «River Training and Ecological Enhancement Potential Using In-Stream Structures.» Journal of Hydraulic Engineering, 2010: 136,967.

Robinson, K. M., Rice, C. E., and Kadavy, K. C. (1997). “Design of rock chutes.” ASAE Paper No. 972062, St. Joseph, Mich.

Roni P, T. J. Beechie, R. E. Bilby, F. E. Leonetti, M. M. Pollock, and G. R. Pess. «A review of stream restoration techniques and a hierarchical strategy for prioritizing restoration in Pacific northwest watersheds.» North American Journal of Fisheries Management, 2002: 22(1), 1-20.

Rosgen, D.L. (2001). “The Cross-Vane, W-Veir and J-Hook Vane Structures: Their Description, Design and Application for Stream Stabilization and River Restoration.” Proc., Wetland Engineering and River Restoration Conf.(CD-ROM), ASCE, Reston, Va.

Rosgen, David L.(2006). "The Cross-Vane, W-Weir and J-Hook Vane Structures...Their Description, Design and Application for Stream Stabilization and River Restoration." Paper delivered at American Society of Civil Engineers Conference, Reno, NV, 2001; updated 2006.

Rosgen, Dave (1996). Applied River Morphology. 2nd ed. (Fort Collins, CO: Wildland Hydrology, publ.) ISBN 978-0-9653289-0-6.

70

Scurlock, S.M., Thornton, C. I. and Abt S. R. (2011). “One-Dimensional Modelong Techniques for Energy Dissipation in U-Weir Grade-Control Structures.” World Environmental and Water Resources Congress, ASCE, 2496-2507.

Scurlock, S.M., Cox, A. L., Thornton, C. I. and Baird, D. C. (2012). “Maximum Velocity Effects from Vane-Dike Installations in Channel Bends.” World Environmental and Water Resources Congress,, ASCE, 2614-2626.

Scurlock, S.M., Thornton,C. I. and Abt S. R. (2012). “Equilibrium Scour Downstream of Three-dimensional Grade-control Structures.” J. Hydraul.Eng., ASCE, 138(2), 167-176.

Shields, F. D., JR, Knight, S. S. and Cooper, C. M. (1995). “Incised Stream Physical habitat Restoration with Stone Weirs.” Regulated rivers: Research and Management, Vol. 10, 181-198.

United States Department of Agriculture, Natural Resources Conservation Service Part 654 Stream Restoration Design, National Engineering Handbook, Chapter 11 Rosgen Geomorphic Channel Design, Issued August 2007.

Veronese, A. (1937). “Erosioni di fondo a valle di uno scarico.” Annali. dei Lavori Pubblci., 75(9), 717–726 (in Italian).

Washington Department of Fish and Wildlife (WDFW); U.S. Fish and Wildlife Service, (2004). "Fluvial Geomorphology." Stream Habitat Restoration Guidelines.

Whittaker, W., and Jaggi, M. (1996). “Blockshwellen.” Mitteilungen 91, Versuchsanstalt fur Wasserbrau, Hydrologie und Glaziologie, ETH, Zurich, Switzerland.

ACKNOWLEDGMENTS

Thanks to the technicians of the Hydraulic Laboratory of University of Pisa: Alessandro, Antonio, Nicola and Vincenzo, for the kindness, sympathy and essential help in the realization of the model and installation of equipment;

Thanks to Professor Stefano Pagliara, for his precious guidance;

Thanks to Dr. Eng. Michele Palermo for his helps as a kind close friend;

Thanks to my wife “Leila” for her lovely supports and her kind helps with patience.

Thanks to my kind parents and my lovely family.

Thanks to my friends, without you, even for the smallest thing, I would not be able to do;