Stream Restoration Raccoon Creek A Case Study

Transcription

1 Stream Restoration Raccoon Creek A Case Study Restoration of a Degraded Stream System Steven Glickauf

2 Presentation Overview Stream Restoration Raccoon Creek Restoration Site Case Study Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation Stream Construction and Post Construction Photos

3 What is Stream Restoration? Uses Natural Channel Design Techniques to Restore Natural Hydrologic and Sediment Transport Functions to a Stream While Accounting for its Current Watershed Conditions A Stable Stream Moves the Sediment and Water Generated by its Watershed while Maintaining Dimension, Pattern, and Profile without Aggrading or Degrading

4 Traditional Design vs. Natural Channel Design

5

6 Loss of Function wr_rsa_2785.jpg

7 Improved sediment transport Restore Function Reconnect stream to floodplain Improve Bedform Diversity and Habitat

8 What is a Stable Stream? A Stable Stream Moves the Sediment and Water Generated by its Watershed while Maintaining Dimension, Pattern, and Profile without Aggrading or Degrading

9 Lane s Diagram

10 Bankfull Discharge Bankfull Q Fills a stable channel up to the elevation of the active floodplain. Represents a breakpoint between processes of channel formation and floodplain development. Assumed to be equal to Effective Q and Dominant Q. Typically has a return period of years (1.5 commonly quoted)

11 Presentation Overview Stream Restoration Raccoon Creek Restoration Site Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation Stream Construction and Post Construction Photos

12 Raccoon Creek Restoration Raccoon Creek is one of TNC s high priority watersheds in the Greater Etowah Watershed Supports one of the largest populations of Cherokee darter in species genetically distinct lower evolutionary species unit Purpose of project is to improve aquatic habitat for the Etowah and Cherokee Darters through the restoration, enhancement and stabilization of ~ 6,441 feet of channel. Phase 1 completed March 2011 Phase 2 completed February 2013

13 Design Considerations Primary goal was to reduce bank erosion Secondary goal was to create and improve habitat for the both the Etowah and Cherokee Darter Design Considerations Re-establish a floodplain Bank stabilization Addition of structure for habitat and stability Riparian reforestation

14 Etowah Darter Federally Endangered Preferred habitat is riffles, typically in moderate to strong current Gravel and cobble substrate Occurs in the main channel of the Etowah River and in larger tributaries Sensitive to sediment Etheostoma etowahae, Fed E

15 Raccoon Creek Overview

16 Cherokee Darter Federally threatened Know from only about 20 streams in the Etowah basin Prefers small streams and can be found in small pools and in runs/riffles over coarse gravel and cobble Etheostoma scotti, Fed T Photo by Bud Freeman

17 Raccoon Creek Overview

18 Steps for Developing a Restoration Project Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation

19 Existing Conditions Drainage Areas of: Darter Creek: 0.1 mi² Raccoon Creek: 23.6 mi² Suburban and Forested Watershed Sites Located within Georgia Power Company Right of Way

20 Existing Conditions Assessment

21 BEHI & NBS Analysis EPA Accepted Method for Developing Sediment TMDL (WARSS) Statistically Valid Method for Predicting Bank Erosion Rates

22 Unstable Bank High BEHI Stable Bank Low BEHI BEHI Assessment with NBS will provide an approximate sediment contribution for the reach assessed in tons/year

23

24 Longitudinal Profile Raccoon Creek Elevation Thalweg Water Surface 680 Top of Bank Station

25 Cross Sections

26 Bed Materials 100 Raccoon Creek Pebble Count Particle Distribution Silt/Clay Sand Gravel Cobble Boulder Bedrock 70 Percent Cumulative (%) Particle Class Size (mm) Reach Summary Riffle Summary Pool Summary

27 Geomorphic Results Each stream has Bank Height Ratios, indicative of severe incision stream type Existing Conditions Notation Units minimum maximum average drainage area DA sq mi Mannings Roughness Coefficient "n" bankfull discharge Q bkf cfs Cross-Section Features bankfull cross-sectional area A bkf SF average velocity during bankfull event v bkf fps width at bankfull w bkf feet riffle maximum depth at bankfull d max feet riffle mean depth at bankfull d bkf feet bankfull width to depth ratio (W/D) w bkf /d bkf riffle max depth ratio d max /d bkf max tob d maxtob feet bank height ratio BHR feet/feet floodprone area width w fpa feet entrenchment ratio (Wfpa/Wbkf) ER feet/feet C5

28 Steps for Developing a Restoration Project Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation

29 Bankfull Verification Field Verification of bankfull in ungauged watershed Aid in designing new channels Know your watershed Know that rainfall/runoff drives the relationship Gage Station Survey Reference Reach Survey Regional Curves

30 Reference Reach Surveys 2 Onsite Reaches Used Reach 1 Drainage Area: 23.6 mi² Cross Sectional Area: 130 ft²

31 Gauge Station Survey Hurricane Creek Drainage Area: 0.33 mi² Bankfull Discharge: 50cfs Return Interval: ~1.5 years Cross Sectional Area: ft²

32 Regional Curve Developed by Dunne and Leopold in 1978 Relates dependent variables such as cross sectional area, width, depth, and discharge versus the independent variable of drainage area Used as a tool to help verify bankfull stage, and as an aid in design No published GA Piedmont Regional Curve GA Coastal Plain Regional Curve is available, however, the project is in the Piedmont

33 1000 GA Corblu y = x R 2 = NC and GA Rural Piedmont Regional Curve NC y = x R 2 = Bankfull X-Sec. Area (Sq. Ft.) Lower 95 % Upper 95% GA NC Raccoon Creek NC Piedmont GA Piedmont* Watershed Area (Sq. Mi.)

34 Steps for Developing a Restoration Project Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation

35 Design Criteria Selection Design Criteria Selection YES Is there a reference reach upstream with a stable riffle and the same valley slope? NO Reference Reach Survey Reference Reach Ratios as Design Criteria Reference Reach Database Review Ratios Reference Reach Search Reference Reach Survey If Possible Ratios Regime/Literature Review Equations Regime Equations Past Project Evaluation Review of Monitoring Data Regime Equations and Ratios Select Design Ratios and Equations

36 Design Criteria Raccoon Creek Design Notation Units minimum maximum average stream type drainage area DA sq mi C Mannings Roughness Coefficient "n" bankfull discharge Q bkf cfs Cross-Section Features bankfull cross-sectional area A bkf SF average velocity during bankfull event v bkf fps width at bankfull w bkf feet riffle maximum depth at bankfull d max feet riffle mean depth at bankfull d bkf feet bankfull width to depth ratio (W/D) w bkf /d bkf riffle max depth ratio d max /d bkf max tob d maxtob feet bank height ratio BHR feet/feet 1 1 floodprone area width w fpa feet entrenchment ratio (Wfpa/Wbkf) ER feet/feet Sinuosity valley slope S v alley feet/ foot channel slope S channel feet/ foot sinuosity K Riffle Features riffle slope S riffle feet/ foot riffle slope ratio S riffle /S channel Pool Features pool slope S pool feet/ foot pool slope ratio S poo l/s channel pool-to-pool spacing L p-p feet NA NA pool spacing ratio L p-p /w bkf NA NA maximum pool depth at bankfull d pool feet pool depth ratio d pool /d bkf pool width at bankfull w pool feet pool width ratio w pool /w bkf pool cross-sectional area at bankfull A pool SF pool area ratio A bkf /A pool

37 Sediment Transport Analysis Test for aggradation or degradation potential Competency analyses Capacity analyses

38 Sediment Transport Analysis Sand/Gravel Bed Stream Competency analyses performed Raccoon Creek Shear Stress Analysis Existing Conditions Design Bankfull Discharge (cfs) Bankfull Xsec Area, Abkf (sq ft) Bankfull Width, Wbkf (ft) Bankfull Mean Depth, Dbkf (ft) W/D Ratio Wetted Perimeter, WP=W+2D (ft) Hydraulic Radius, R (ft) Schan (ft/ft) Boundary/Bankfull Shear Stress, t (lb/sq ft) d50 of pavement 100 ct (mm) Subpavement Bar sample Subpavement Bar sample d50 of bar / subpavement (mm) di = D100 of bar / subpavement (mm) di = D100 of bar / subpavement (ft) ratio - d50pavem / d50subpavem 0.06 #DIV/0! 0.06 #DIV/0! ratio - di / d50 pavement ci-equation

39 Hydraulic Analysis Existing versus design water surface profiles Design stage / discharge relationship Existing versus design shear and power versus discharge relationships

40 Morphological Measurements and Ratios Pattern (Plan View) Belt Width Thalweg (Channel Length) Radius of Curvature (Rc) Meander Length (Lm) Channel Pattern Measurements Meander Length (Lm) Radius of Curvature (Rc) Belt Width (Wblt) Valley Length (VL) Channel Pattern Calculations Ratio: Radius of Curvature/Riffle Width (Rc/Wr) Ratio: Meander Length/Riffle Width (Lm/Wr) Meander Width Ratio (MWR=Wblt/Wr) Sinuosity (K) = Channel Length/Valley Length

41 Steps for Developing a Restoration Project Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation

42 Design

43 Design

44 Design

45 Proposed Cross Sections

46 Proposed Profile

47 Steps for Developing a Restoration Project Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation

48 Permitting USACE 404 Stream Buffer Variance LDP NPDES CLOMR/LOMR

49 Steps for Developing a Restoration Project Existing Conditions Assessment Bankfull Verification Design Criteria Selection Design Permitting Construction Evaluation

50 Darter Creek : Construction January 2011

51 Darter Creek : Post-Construction bankfull rain event

52 Raccoon Creek Site # 3 : Pre-Restoration

53 Raccoon Creek Site # 3 : Construction January 2011

54 Raccoon Creek Site # 3: Post-Construction bankfull rain event

55 Raccoon Creek Site # 3: Post-Construction

56 Raccoon Creek Site # 4: Pre-Restoration

57 Raccoon Creek Site # 4: Construction

58 Raccoon Creek Site # 4: Post-Construction bankfull rain event

59 Raccoon Creek Site # 4: Post-Construction

60 Raccoon Creek Site # 5: Pre-Restoration

61 Raccoon Creek Site # 5: Construction (Jan-Feb, 2013)

62 Raccoon Creek Site # 5: Post-Construction ( )

63 Raccoon Creek Site # 5: Bankfull Rain Event ( ) (day before) (after water receded)

64 Raccoon Creek Site # 5: Post Construction

65 Raccoon Creek Site # 6: Pre-Restoration

66 Raccoon Creek Site # 6: Construction (Jan-Feb 2013)

67 Raccoon Creek Site # 6: Post-Construction (Feb 2013)

68 Raccoon Creek Site # 6: Post-Construction

69 Raccoon Creek Site # 8: Pre-Restoration Curb in culvert

70 Raccoon Creek Site # 8: Post-Restoration Curb cut (~10 ) to enhance fish passage

71 QUESTIONS? Etheostoma scotti Etheostoma stigmaeum Etheostoma etowahae Darters, from top left: Cherokee, Speckled, & Etowah (center)