Fish Passage at Road Crossings

Transcription

1 Fish Passage at Road Crossings 1

2 Crossing Design Workshop Outline 1:00 to 2:00 Intro, Design Overview, Channel Width 2:00 to 2:15 Break 2:15 to 3:15 No-Slope, Stream Simulation Design 3:15 to 3:30 Break 3:30 to 4:30 Bridges, Channel Profile, Project Plans, SS Monitoring 4:30 to 5:00 Questions, Wrap up 2

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5 Culvert-related Regulations RCW A dam or other obstruction across or in a stream shall be provided with a durable and efficient fishway approved by the director. The fishway shall be maintained in an effective condition and continuously supplied with sufficient water to freely pass fish. 5

6 What is a barrier 1. No fish pass upstream ever 2. Assessment criteria (level A) A. Outfall drop > 0.8 ft B. Slope > 1% C. Width < 75% BFW D. Countersunk < 20% 3. Design criteria 6

7 WDFW Culvert Inventory culverts on fish bearing streams 33% Passable 56% Barriers Level A & B criteria 11% Barrier status unknown 7

8 Extrapolated from current data, there are approximately 33,000 passage barriers in Washington State. 8

9 Fish Passage Progress* Year Barriers Corrected Total 3,513 * Governor's Salmon Recovery Office (2008) 9

10 Effectiveness of WDFW s Hydraulic Project Approval (HPA) Permit in Maintaining Fish Passage at Road Crossings (Price, et al.) * Permit Year Barriers Nonbarriers % Barriers 2007 (n=20) % 2003 (n=32) % 1998 (n=25) % Total (n=77) % *In press: North American Journal of Fisheries Management, October,

11 Effectiveness of WDFW s Hydraulic Project Approval (HPA) Permit in Maintaining Fish Passage at Road Crossings Meet NS or SS design criteria 30 39% Do not meet design criteria 45 58% Failed 2 3% Total % 11

12 Ecological Benefits Hydraulic Method Stream Simulation Floodplain Continuity Valley and Floodplain Processes Flood capacity Crossing structure width 12 adapted from Bates, 2003

13 Culvert width in relation to flood plain 100 yr flood Bankfull flood Natural channels have a bankfull channel an overflow surface or flood plain, of varying extent 13

14 Culvert width in relation to flood plain Hydraulically designed culvert Passes flood flows Allows passage of certain fish, certain flows Many undesirable ecological effects 14

15 Culvert width in relation to flood plain Channel width culvert Passes flood flows and debris Allows passage of most fish Allows some stream processes 15

16 Culvert width in relation to flood plain Stream Simulation culvert Passes flood flows and debris Allows passage of nearly all fish and aquatic organisms Allows many stream processes (including banks) 16

17 Culvert width in relation to flood plain Full spanning bridge Passes flood flows and debris Allows passage of all fish Allows all stream and flood plain processes 17

18 Road Crossing design process Is a permanent crossing necessary? Crossing Siting Habitat considerations Culvert Bridge No slope design Hydraulic design Stream Simulation design Design 18

19 Bear Ck. No Slope Method 19

20 Hydraulic method Retrofit with baffles WF Hylebos Ck. 20

21 Club Ck. Stream Simulation Method 21

22 Bridges Nearly competed Bridge Design for Habitat Protection Channel width > 15 ft Reach analysis recommended Site specific design procedure 22

23 Channel Width For low slope, alluvial channels Use bankfull width For high slope, non-alluvial (bedrock, armored), incised channels Use channel width indicators Measure a minimum of three typical widths in a freely flowing alluvial reach or one where natural stream processes prevail. 23 Appendix H, P. 100

24 Bankfull flood event Average velocity = 5 fps Width of channel = 13 feet Discharge = 80 cfs Actively mobile bed Xtrb Salt Ck. WRIA 19 24

25 Channel Width Bankfull width Flood Plain 25

26 YN Toppenish near bankfull

27 Bankfull flow Asotin Ck 27

28 Channel Width Indicators Indications of minimum bankfull depth Height of depositional features Undercuts in the bank 28

29 Depositional features and Undercut banks 29

30 Channel Width Indicators Change in vegetation Change in slope 30

31 BF width = 21 ft Entrenchment ratio = 1.5 Slope = 1.6% Q BF = 157 cfs Q 2 = 194 cfs

32 Surveyed cross section BFD Stage hydrograph Oct-Feb,

33 BFW BFW = 6 Entrenchment ratio = 1.2 Slope = 14% Q BF = 10 cfs Q 2 = 12

34 Channel Width Indicators Soil Gravel 5. Change in the particle size 6. Stain lines Questionable value 34

35 Where to measure channel width Measure width outside the influence of the existing culvert Avoid backwatered reaches (dense vegetation, beaver dams, etc.) Avoid modified reaches (dikes, channelization, etc.) Avoid grade control structures. Avoid sharp bends and accumulations of LWD. 35

36 Alternatives to direct channel width measurement Wide, flat wetland with an ill-defined channel, backwatered by vegetation, wood and beavers is a challenging situation for determining channel width. Regional regression prediction of stream width. Calculation of bankfull flow from regional regression equations (USGS) with a manning s equation approximation of channel width. 36

37 Channel width regional regression 60 W ch =0.95A 0.45 P calculated channel width y = x R 2 = W. Wash Hi gradient Coarse bed measured channel width

38 Channel width regional regression Independent data set, 34 additional steams calculated channel width y = x R 2 = measured channel width

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40 Strictly for fish passage, culvert shape does not matter. The differences are in regional preferences, constructability, cost and construction impacts. 40

41 No Slope Option 1. Culvert at flat gradient 2. Culvert bed width equal to channel bed width 3. Minimum downstream countersink 20% of rise 4. Upstream countersink 40% of rise maximum 41 Chapter 4, P. 17

42 No-slope option General application b.i is a WAC rule, not an engineering method. New and replacement culverts Simple installations; low to moderate natural channel slope (generally, <3%) and short culvert length (generally, <75 ft.) No target species; passage for most species No special fish passage design expertise or survey information required (for fish passage design) 42 Chapter 4, P. 17

43 General streambed material specification Culvert fills should be: Appropriate for the slope and discharge of the stream Well-graded, with all size classes represented below the maximum size (fines, sands, gravel larger sizes as needed) Include at least 5% but less than 10% fines Replicate the upstream channel bed, if applicable Rounded, stream-like, material A more detailed discussion of this topic will occur in the Stream Simulation section These recommendations are not in the WAC for the no-slope method. 43

44 Bankfull channel width No-slope option; Information needed Natural channel slope outside the influence of the culvert Evaluation of headcut impacts (for replacements) Elevation of natural channel bed at the culvert outlet 44

45 Under-sized culvert halts sediment and debris transport, induces u/s channel widening and d/s channel scour. 5 ft Upstream channel width = 9ft 45 North Fork Secret Ck.

46 Culvert Design Stream simulation option Simulate adjacent natural channel Premise: If fish can move through natural channel they can move through simulated channel in a culvert. Application All species Resolves most ecological issues Requires detailed engineering design New and replacement culverts Moderate to high channel slope and culvert length Narrow stream valleys 46 Chapter 6, P. 29

47 Stream Simulation Culvert Design Road fill Profile view Countersunk 30-50% of culvert rise. Plan view Channel Width 47

48 Flow isolated from hydraulically smooth culvert wall Good flood width Club Ck. Width ratio = 1.4 Slope = 6.8% Dry bank at most flows Low velocity margin 48

49 Stream Simulation Design Procedure 1. Determine suitability of the site. 2. Determine major characteristics of natural channel; width, floodplain utilization, pool spacing, bed composition 3. Adjust the profile. 4. Design the culvert; dimensions, slope, burial. 5. Design the culvert bed and its transition to the natural channel 49

50 Determine Suitability of the Site Not Suitable Wood dominated Unstable Suitable Sediment controlled Stable 50

51 Channel must be in equilibrium within the culvert s capacity to accommodate change Reduced culvert capacity Aggrading channel 51

52 Channel must be in equilibrium within the culvert s capacity to accommodate change Degrading channel Exposed culvert bottom Headcut or general channel incision 52

53 Stream Simulation Width Criteria Width of bankfull channel 1.2 x Width of bankfull channel + 2 ft Significant inlet contraction or long culvert may require a larger pipe size. 53

54 Slope Ratio Slope ratio = Culvert bed gradient U/S Channel gradient Slope ratio must be less than or equal to Slope ratios > 1.25 represent a change in channel type, not simulation of the adjoining channel. 54

55 Low Slope Stream Simulation LOW GRADIENT (less than 4%) Rosgen type C, E, or F Alluvial gravel bed Pool-riffle morphology 55

56 Low Slope Stream Simulation Bed Slope < 4.0% Well-graded rock bands (D 100 = 1 to 2 times bed D 100 ) to control initial shape Well-graded, not stratified, native streambed sediment mix 56

57 Rock Bands Rock bands Streambed material Min 25 feet Min 25 feet Space the lesser of: 5 times the width of channel or max. vertical difference between crests < 0.8 feet 57

58 Rock Bands Crest of rock bands have a streambed shape 58

59 Low slope without bands 59

60 Darby Ck. rock bands just after construction 60

61 Darby Ck. rock band during first flood. Band has altered but flow is centered and a pool has formed downstream of it. 61

62 High Slope Stream Simulation Bed Slope > 4.0% Well-graded, not stratified, native streambed sediment mix. Step-pool profile. 62

63 High Slope Stream Simulation HIGH GRADIENT (greater than 4%) Rosgen type A, B, some F, G Cobble-boulder bed Very stable Step-pool morphology 63

64 WF Stossel Ck. Big Bob Width ratio = 1.8 Slope = 6.4% 64

65 No channel features built into bed. Slope = 7% 10 Mile Ck. 65

66 Abby culvert, Xtrib. Sherman Ck. Culvert bed slope 14% 10 feet diameter Elevated flood flow 66

67 Bea Culvert, Xtrib Sherman Ck. Culvert bed slope 11% 13 ft diameter At flood flow 67

68 Stream Simulation Bed Design Use natural channel in new installations If the channel is in equilibrium and slope is maintained by sediment, use natural channel gradation to duplicate in culvert. Pebble count of natural channel to determine D 84. Use D 84 to size designed bed. Increase size distribution for Inlet contraction Increased slope If the channel is controlled by debris 68 Chapter 6, P. 33

69 Well-graded Bed Material count Fines Sand Gravel Cobble Boulder 69

70 Bed Material Size Recommended size ratios: D 84 /D 100 = 0.4 D 84 /D 50 = 2.5 D 84 /D 16 = to 10% fines 70 Chapter 6, P. 36

71 Bed Material Size For example, if D 84 = 1.0 feet then: D 16 = 0.13 ft D 50 = 0.4 D 84 = 1.0 D 100 = 2.5 General percentages: 16% small gravel and fines 34% gravel 50% cobble and boulder 71

72 Sample mix 1 scoop bank run dirt 4 scoops 4 minus pit run 4 scoops 8 minus cobbles 2 scoops 1.5 minus rock 1.5 to 2.5 foot rock added during installation 15% slope culvert 72

73 15% slope culvert Step-pool structure painted on wall 73

74 Taylor Ck. 74