DEVELOPMENT OF A HYDRO-GEOMORPHIC MODEL FOR THE LAGUNA CREEK WATERSHED
Agenda Background Hydro-Geomorphic Modeling Methodology HEC-HMS Modeling How is the Model Used
Background Proposition 50 Grant Funding County of Sacramento, Urban Creeks Council, Laguna Creek Watershed Council, Upper Laguna Creek Collaborative Purpose Development of a Watershed Management Plan to protect the natural resources of Laguna Creek, while allowing continued economic development Geosyntec Scope Evaluate existing hydrologic and geomorphic character of the watershed and stream system Developed a Hydro-Geomorphic Model to: Evaluate hydrologic conditions-of-concern Identify, evaluate and recommend effective management strategies
Hydrologic Conditions-of of-concern (Hydromodification) Changes in: the proportion of storage, overland flow and sub-surface recharge the seasonal water balance and timing of stream flows the magnitude, frequency-of-occurrence and long-term duration of flows Resulting in channel erosion and impairment of beneficial uses affecting wildlife life cycle needs for breeding, rearing, and survival
Consequences of Hydromodification Intensified sediment transport and erosion processes Observed as excessive erosion, incision and widening Thompson Creek Santa Clara Valley
Location of Laguna Creek Watershed
Agenda Background Hydro-Geomorphic Modeling Methodology HEC-HMS Modeling How is the Model Used
Elements of the Hydro-Geomorphic Model Characterize the Physical Setting History, climate, physiography, geology, soils Imperviousness & connectivity Geomorphic Assessment Understand character and sensitivity Surveys, bed/bank material, vegetation density Hydrologic Modeling Calibrated, long-term continuous simulation Pre-urban, existing and post-development Channel Modeling Hydraulics, work done and sediment transport Erosion Potential (Ep) Evaluate potential instability, compliance and/or design
Conceptual Layout Q f = time series of flows Q s = time series of transport Hydrologic model Catchment boundary Q f Q s Sediment transport / work model Watershed wide cumulative assessment at multiple cross sections throughout study area
Cross Section Locations in Laguna Cross sections located to allow evaluation of catchment scale, soil s types, existing stream conditions, and development patterns Multiple cross sections allow computation of Ep throughout study area
Hydraulic & Shear Stress Model Q A = 1. 49 K S K = R n 2/ 3 τ avg = ρgr avg S 96 95 94 93 92 91 90 89 88 1.0 0.6 A 1 A 2 R R 0.3 P 2 P 3 P 4 τ b = τ avg n n b avg 2 3 n b = roughness coefficient n avg = composite roughness coefficient 87 0.0 10.0 20.0 30.0 40.0 50.0
Effective Work & Sediment Transport Models Work Consolidated Bank Material n = a 1 n = V 1 ( τ τ ) b b c ( τ τ ) b c Andrew Simons, Ph.D., National Sedimentation Laboratory Derek Booth, Ph.D., WSU Transport Bed Material n τ = b τ c 1 n 1 ( * τ ) 1. 5 = 8 b 0.047 Wilcock-Crowe Equation Meyer-Peter, Muller
Effective Work and Transport Relative to the most Susceptible Boundary Material & Integrated over Time Applied Shear Stress τ W ( ) bi c t bi n = i= 1 τ τ 1.5 τ c Qc τ cbed Erosion Potential (Ep( Ep) Determine which is least resistant Shear Stress Post-Urban Pre-Urban Ep = W W post pre τ c Effective Work Time: 50-year record
EROSION POTENTIAL Measure of Relative Change between Pre- and Post- Conditions Integrates hydrologic change with geomorphic processes Ep = Cumulative Erosive Energy on the most susceptible channel boundary in the Post-Condition Cumulative Erosive Energy on the most susceptible channel boundary in the Pre-Condition
Agenda Background Hydro-Geomorphic Modeling Methodology HEC-HMS Modeling How is the Model Used
Hydrologic Model ACE Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) Continuous simulation Calibration / Verification
HMS Model Set-Up Land Use Pre, Existing, and Future Catchment Delineation Surface Area, Percent imperviousness, Time of Concentration Rainfall-Runoff Soil Moisture Accounting method Clark Unit hydrograph method Linear reservoir baseflow method Routing Muskingum-Cunge Climate Long term continuous records (Sac. Co. & NCDC) Monthly average evapotranspiration (CIMIS)
Continuous Simulations Important Features Simulates soil moisture and antecedent conditions Incorporates the full probability distribution of storms Produces most realistic stream flows for work and transport computations Allows for analysis of distributions as opposed to discrete events Produces time series for better BMP design
Existing Land Use Catchment Area = 31.7 sq.mi Percent Imperviousness = 8%
Future Land Use Catchment Area = 31.7 sq.mi Percent Imperviousness = 22%
Sub-Catchments, Cross Section Locations Multiple cross sections allow computation of Ep throughout study area
Conceptual Rainfall Runoff Model Et Storage Vernal Pool Surface runoff Duripan Interflow Laguna Creek
Soil Moisture Accounting Module SMA Parameters used in Upper Laguna Creek Canopy Storage = 0.08 in Surface Depression Storage = 0.30 in Average Infiltration/Percolation = 0.06 in/hr (U.L.C. watershed 86% Type D soils) Soil Storage Capacity = 6.0 in Tension Zone Capacity = 4.8 in GW1 Storage Capacity = 50 in GW1 Storage Coefficient = 200 hrs
Muskingum-Cunge Routing Sources of reach data: Sacramento County DWR HEC-RAS model (2004) Geosyntec Consultants Survey Data William Lettis & Associates Survey Data USGS Topographical Maps Averaged over reach
Precipitation and Flow Gages Flow Gage Model calibrated at two flow gage locations in study area Flow Gage
Calibration at Waterman Road 2000 1800 Waterman-Bond Gage Model Output 1600 1400 Discharge (cfs) 1200 1000 800 600 400 200 0 11/1/96 12/1/96 12/31/96 1/30/97 3/1/97 3/31/97 Date Peak-weighted Root Mean Square Error function used to compare model output o to flow-gage data.
Cumulative Runoff Volume (ac-ft) Calibration & Verification at Waterman Road 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 Waterman-Bond Gage Model Output ± 5% in volume 0 10/1/96 4/1/97 10/1/97 4/1/98 10/1/98 4/1/99 10/1/99 3/31/00 9/30/00 Date 2000 Cumulative Volume Flow Duration Waterman-Bond Gage Model Output 1500 Discharge (cfs) 1000 Calibration Period: 10/1/96-9/30/98 Verification Period: 10/1/98-9/30/00 500 0 1 10 100 1,000 10,000 100,000 Duration (hrs)
Flood Frequency Results: Verification of Existing Condition 3,000 Flood Frequency Distribution For Laguna Creek at Waterman-Bond HEC-HMS Existing Condition: Partial Duration Series HEC-HMS Existing Condition: Log-Pearson Type III 2,500 David Ford Study: 'Current Condition' USGS Gage 11336585 @ Waterman: Log-Pearson Type III (11-yrs of data) 2,000 Discharge (cfs) 1,500 1,000 500 0 1 10 100 475 14th Street, Suite 400 Oakland, CA 94612 Recurrence Interval (Years)
Agenda Background Hydro-Geomorphic Modeling Methodology HEC-HMS Modeling How is the Model Used
How is the Model Used Evaluate changes in hydrology Evaluate changes in work and transport Identify the range of flows to manage i.e., Geomorphically significant flows Evaluate potential impacts channel instability, enlargement Identify effective management strategies
Evaluate Seasonal Flow Changes Predicted Changes in Seasonal Stream Flow Volumes 100% Percent Change from Existing Conditions 80% 60% 40% 20% 0% -20% Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 475 14th Street, Suite 400 Oakland, CA
Example, Cross Section WLA-3 Future Imp = 28% Slope = 0.002 τc = 0.20 lbs/sq-ft Broad shallow channel (high W/D ratio), frequent access to floodplain, shallow gradient, vegetated banks Predicted Ep = 1.6 (60% increase)
Evaluation of Work Done Distribution of Work Done at Cross Section GS XS-9, LC30 225000 Total Work Done (ft-lbs/sq-ft) 200000 175000 150000 125000 100000 75000 50000 Q 2 Q 10 Pre-Development Future Development 25000 0 0 20 40 60 80 100 120 140 160 180 Discharge (cfs) 475 14th Street, Suite 400 Oakland, CA
Range of Flows to Manage (Determined from Cumulative Work Curve) Qc to the 10-year event 110% Cumulative Frequency Distribution of Sediment Load Cross Section XS-9, Laguna Creek 100% Percentage of 50-Year Total 90% 80% 70% 60% 50% 40% 30% 20% Qc 2-Year Peak Illustrates importance of managing flows less than the 2-year peak flow 10-Year Peak +90% of total load is transported by flows less than the 10-year peak flow 10% 0% Qc = 20% of the 2-Year Peak Flow 0 20 40 60 80 100 120 140 Discharge (cfs) 475 14th Street, Suite 400 Oakland, CA
Evaluating Potential Impacts & Effectiveness of Controls Specify In-Stream Management Objective Ep = 1 ± 20% Maintains a baseline work and sediment transport capacity Links development and hydrologic change to geomorphic processes
Reach 1 Reach 2 Reach 3 Reach 4 Reach 4 Location Evaluate Potential Impacts under Slope Future Conditions Future %IMP Erosion Potential Critical Erosion Potential by Reach (Ep) Shear Stress WORK INDEX Mean Median Std Dev (lbs/sqft) (unitless) (ft-lbs/sqft) (ft-lbs/sqft) (ft-lbs/sqft) (ft-lbs/sqft) G.S. XS-1 1.0% 5.2 1.04 1.04 1.04 1.04 G.S. XS-2 1.0% 15.6 0.38 1.47 1.47 G.S. XS-3 0.60% 11.4 1.27 1.28 1.34 1.28 0.11 G.S. XS-4 0.60% 11.4 1.26 1.27 G.S. XS-5 0.50% 47.3 1.89 1.93 2.06 2.10 G.S. XS-9 0.40% 49.4 0.20 2.24 2.32 G.S. XS-6 0.10% 28.8 1.64 1.66 G.S. XS-7 0.15% 28.8 1.61 1.64 1.58 1.60 0.09 WLA Site 1 0.10% 29.0 1.55 1.57 WLA Site 2 0.20% 27.5 1.46 1.46 WLA Site 4 0.24% 25.2 1.41 1.41 WLA Site 6 0.35% 25.2 0.38 1.41 1.42 1.41 1.42 0.01 WLA Site 7 0.22% 25.2 1.42 1.42 WLA Site 8 0.24% 25.2 1.40 1.40 WLA Site 10 0.07% 25.2 1.61 1.60 WLA Site 12 0.07% 25.4 0.20 1.43 1.43 1.47 1.44 0.09 WLA Site 13 0.07% 25.4 1.45 1.45 WLA Site 15 0.10% 26.3 1.42 1.41 WLA Site 16 0.07% 25.5 1.37 1.37 WLA Site 17 0.10% 25.5 0.18 1.37 1.39 1.36 1.36 0.04 WLA Site 18 0.06% 25.2 1.33 1.35 G.S. XS-8 0.05% 22.1 1.28 1.31 Trib.1 WLA Site 19 0.15% 12.5 1.10 1.11 1.11 1.11 Trib.1 WLA Site 20 0.15% 12.5 1.11 1.11
Flow Control Effectiveness (Santa Clara Results, 2005) Probability of Instabilities 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Hydrograph Matching Q= 1 / 10 2-yr Q= 1 / 2 2-yr Peak flow control Flow Duration Control is effective at meeting objective -5 0 5 10 15 20 25 30 Erosion Potential (Ep) Post-Urban 44% IMP Selected Threshold
Flow Duration Control Design Concept Retains the increase in runoff volume Allowable low flow discharge (Qc) = 25% of the 2-year peak flow Stream discharge matches the frequency distribution to the predeveloped condition for flows above Qc Overflow Stream Discharge Matched FDC Inflow Capture Volume Qc Infiltration, diversion, by-pass
Example Flow Duration Curve Matching Discharge (cfs) 200 180 160 140 120 100 80 60 40 20 0 Critical Flow Criteria (Qc) Flow Duration Matching Curve Upper Laguna Creek Watershed 1 10 100 1,000 10,000 100,000 Hours of Flow Greater Than or Equal to Discharge Infil = 0.14 in/hr Existing Conditions Future Development FDC Basin Discharge Increased runoff volume discharged under Qc 475 14th Street, Suite 400 Oakland, CA 94612
Example Runoff Time Series with Flow Duration Control 225 Infiltration = 0.14 in/hr. % Imperviousness = 40% 200 175 150 Pre-Project Runoff Post-Project Runoff Discharge from FDC Basin Discharge (cfs) 125 100 75 50 25 Critical flow (Qc) 0 1/8/95 1/9/95 1/10/95 1/11/95 1/12/95 1/13/95 1/14/95 1/15/95 1/16/95 1/17/95 1/18/95 Time 475 14th Street, Suite 400 Oakland, CA 94612
Sizing Charts for Easier Implementation Total Basin Surface Area (% of project) 6 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 Catchment infiltration rate = 0.20 Catchment infiltration rate = 0.14 Catchment infiltration rate = 0.07 Catchment infiltration rate = 0.02 ZERO BASIN INFILTRATION FDC Basin Sizing Nomograph for Laguna Creek Basin Depth = 6-ft with 3:1 Side-slopes y = 0.030x 1.098 y = 0.035x 1.096 y = 0.060x 0.851 y = 0.065x 0.805 Note difference in area requirements between BMP types Storage in bioretention includes 12-in on surface plus soil pore space. BIORETENTION FACILITY Sizing Nomograph for Laguna Creek 0.5 475 14th Street, Suite 400 Oakland, CA 94612 Percolation rate = 0.20 0 14 0 10 20 30 40 50 60 70 80 Percolation 90 rate = 0.14 100 Basin depth = 6-ft6 Project Percent Imperviousness Bioretention depth = 4-ft4 Surface Area (% of Catchment) 16 12 10 8 6 4 2 Percolation rate = 0.07 y = 0.446x 0.727 y = 0.467x 0.734 y = 0.376x 0.753 0 0 10 20 30 40 50 60 70 80 90 100 475 14th Street, Suite 400 Oakland, CA 94612 Percent Imperviousness
Next Steps Sensitivity Analysis Incorporate Mixed Management Strategies into Model & Evaluate Effectiveness Evaluate need for Large Flood Control Detention Evaluate In-Stream Solutions
Questions? By Gary Palhegyi and Chris Potter For more information gpalhegyi@geosyntec.com cpotter@geosyntec.com (510) 836-3034 3034