STREAM CONDITION & EROSION CONCERNS IN CITY OF FORT WORTH. Ranjan S. Muttiah Stormwater Management City of Fort Worth

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1 STREAM CONDITION & EROSION CONCERNS IN CITY OF FORT WORTH Ranjan S. Muttiah Stormwater Management City of Fort Worth

2 Contrast in Practices AG LAND URBAN LAND - Soil is the livelihood - Soil for building - Prevent soil loss - Out of sight - Continuous - Mostly one time - Floodplain? - Floodplain, YES

3 City Perspective Permits & inspection of construction sites Maintenance agreements Monitor & maintain state of natural channels Monitor dam safety Incentives for BMPs Take WQ initiatives in city SW CIP projects

4 Concerns #1: What have we done? #2: What is the health of streams? #3: How much erosion & sedimentation? #4: What can we achieve? #5:What are the design methodologies & BCA? # 6:What are the opportunities?

5 Concern #1 What have we done?

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9 Channel Protection Silt fence is not appropriate for channel protection

10 CIP Channel Protection Need details and sizes for Check Dams Need more info on plan sheet to review Check Dams

11 CIP Example Check Dams placed at 100 foot intervals Check Dam placed on ridge is unnecessary

12 Spoil Stockpile Should be protected if inactive for more than 14 days

13 Spoil Stockpile Example If not protected can be a major source of sediment Spoil Stockpile Silt Fence will not be adequate Be aware of major channels and floodplains 83

14 Drainage Area Map Construction Exit on high side of project is preferred CIP Construction Exit (s) Avoid Exit on low side of project X

15 CIP BMP Calculations Inlet Protection No details provided for inlet protection Outfall Protection Rock Berms No design calculation provided for outfall protection 60

16 Silt Fence Turn Silt Fence uphill at the ends and at intervals if necessary particularly on linear projects Incorrect Correct 75

17 Silt Fence Stone Overflow required at low point or approximately every 300 feet 73

18 CIP Silt Fence Turn Uphill at end Construction Exit Silt Fence Turn Uphill at regular intervals Silt Fence Directing runoff into channel Turn upstream at ends Turn upstream at regular intervals Provide stone overflow 63

19 Silt Fence Example If not turned uphill at the end, it simply directs runoff and sediment off of site Flow Direction Sediment directed offsite 76

20 Concern #2 What is the health of streams?

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22 Stream Condition Assessment Field Investigation Photograph and Document Conditions Assess Channel Condition Good, Fair, Poor Areas of Imminent Failure Scour at Hydraulic Structures More Detailed Evaluation at City Request

23 Condition Assessment PERCENT Good Fair Poor

24 Average Velocity, ft/s Year 5-Year 10-Year 25-Year 50-Year 100-Year 2 Hjulstrom, Maximum Velocity, ft/s

25 MAX V 2, ft/s DA, miles 2

26 YR 5-YR 10-YR 50-YR 100-YR 2.5 Avg Shear, Lb/sf Max Shear, Lb/sf

27 Concern #3 How much erosion & sedimentation?

28 Lake Como (1889)

29 Lake Como Cesium-137, Half-life = 30.3 YEAR Initial Concentration = 5.1 pci/cm 2 Depth, Ft Interval of deposition = 45 Years Erosion rate = 0.13 inches/year CS-137, pci/cm 2

30 USLE Y (tons/ac/yr) = R*K*(LS)*C*P R = 250 K = 0.32 LS = (2% avg. slope & 100 for sheet flow) C = 1 & P = 1 Erosion rate = 0.26 inches/year Sediment Deliverty Ratio = 0.5

31 Moore & Burch (unit stream power) Log Ct I J 10 log 10 VS w Vcr S w V cr *S = m/s I = 1; J = 2 (adjusted from literature) Using Q 2 flows, d 50 = 30 um Erosion rate = 0.23 inches/year Sediment delivery ratio = 0.56

32 Julien & Simons (1985) q e t 1 S e2 0 q e3 With e 1 = 1.0; e 2 =1.6; e 3 =2 Q 2 flows: Erosion Rate = 0.24 inches/year SDR = 0.48

33 S DR from Boyce (1975) S DR DA 0. 3 Lake Como DA = 2.98 km 2 SDR = 0.3

34 Empirical Methods Isotope methods (Cesium, Lead) Exposed Roots Jet test Old topos & imagery

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36 Jet Test for Erosion Rate

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39 Knick Point Migration

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43 2009

44 Concern #4 What can we achieve?

45 Watershed Controls Sustainable development Stream buffers Bio-filtration, swales, BMPs Low Impact Development

46 Erosion Controls Measures used to retain soil in place Limits of Disturbance Minimize disturbed area Slope Protection Protect steep or erodible slopes Channel Protection Energy Dissipaters, Turf Reinforcement Mats, etc. Temporary Stabilization Required for disturbed areas where work stops for 14 days or more. Final Stabilization Established vegetation and BMPs meeting contract requirements 44

47 Sediment Controls Measures used to trap sediment after broken loose Sediment Barriers Linear controls, sediment basins, etc.) Perimeter Controls Linear BMP at all down slope boundaries Inlet Protection Construction Access Controls Dewatering Controls all pumped water should be discharged through a BMP prior to leaving site 45

48 iswm Construction Plan Erosion Controls Sediment Controls Material and Waste Controls

49 Grading Ordinance Grading Permit or current iswm Plan required for any land disturbance of 0.5 acres or more Required prior to Commercial Building Permit Grading must conform to CFW iswm Criteria Manual 2012 Edition adopted by reference Plans approved under 2006 Manual grandfathered Early Grading Permit allowed prior to development Fill material placed in future ROW subject to inspections

50 Grading Ordinance Grading Certificate required Plan in hand inspection by Owner Prior to Commercial Certificate of Occupancy Single Family grading standards established Subdivision Grading Plan Lot and lot lot grading Grading Permit issued by Development $50 fee charged for Grading Permit Effective Date: 8/1/2012

51 Voluntary Water Quality Standards Detain 1.5 volume for minimum of 24- hour on-site Stream bank protection (1-yr, 24-hour) Limit downstream erosive velocities Bermuda grass <= 6 fps, clays < 5 fps, rock < 15 fps

52 Water Quality Volume WQ ( in.) 1.5* v R v R * I v (%)

53 WQ Release Rate q WQ q u 2 ( cfs / mi / in)* DA( mi )* WQ ( in) 2 v

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55 Evaluate: Scour Stop

56 Evaluate: A-Jack

57 Evaluate: Tumbling Flows

58 Concern #5 What are the design methodologies & BCA?

59 Qeffective vs. Qbankfull

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62 Sediment Transport Methods Bed load - Einstein, Meyer-Peter-Muller Suspended load - Einstein, Lane & Kalinske, Chang,Simons & Richardson Total load - Einstein modified, Ackers & White, Colby, Bagnold, Toffaleti, Yang

63 18 Mary s Creek at Vickery D, ft Einstein(adj.) USGS Rating Curve Hey Bray Bathurst Engelund_Hansen(adj.) RAS ,000 4,000 6,000 8,000 10,000 12,000 14,000 Q, cfs

64 RAS Scour Routines Total Scour = Long Term Aggradation /Degradation (HEC 18) + Contraction Scour + Pier & Abutment Scour Contraction Scour = Clear water Or Live bed scour Pier Scour = CSU or Froehlich Equations Abutment Scour = HIRE & Froehlich Equations

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68 Reach B: Swept Bedrock

69 Reach C: High Erosion Bed Bank

70 Lower C: Transition Planar Bed

71 Reach D: Planar Beds

72 Reach E: Pool Riffle

73 Change in Hydraulic Stability: Regime and Extremal Methods

74 Hydraulic Stability Width Increase: 10 feet Depth Increase: 2 feet

75 Gravel Eroded from Upstream and Deposits Downstream for both Pre developed and Developed Conditions

76 Benefit-Cost Analysis Future without project vs. With project (with $s or indices) Metrics: Eco-system services + physical processes Water quality benefits Value of habitat end-point

77 Concern #6 What are the opportunities?

78 Flood control integrated with WQ benefits (more with more ) Maintenance & life-cycle costs Public amenity Quantify in planning and construction details BCA Funding

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