PWD s Systematic Watershed-wide Approach to Stormwater Mgmt. Jeffrey Featherstone, PhD Director, Center for Sustainable Communities, Temple University Paul DeBarry, PE, PH, GISP, D.WRE Director, Geospatial Data Technologies and Watershed Mgmt., NTM Engineering Joanne Dahme, General Manager Public Affairs, Philadelphia Water Department Richard Fromuth, P.E. Senior Research Associate, Center for Sustainable Communities, Temple University.
Agenda: 1. PWD Watersheds & Studies/Plans 2. Typical Procedure for Development of a Comprehensive Stormwater Management Plan
Coordinated efforts: Act 167 SW Mgmt. Plans GIS Mapping, Watershed Hydrologic Modeling Model Stormwater Ordinance Plan of Action for SW Mgmt. & Retrofitting River Conservation Plans Resource Inventory Management Options (stream clean-ups, protect open space, protect stream corridors) Comprehensive Characterization Reports Water Quality Sampling Habitat Assessment Indicator Status Update Integrated Watershed Mgmt. Plans Restore Impaired Water Quality Multi-faceted Approach (Stream Restoration, BMPs, CSO Rehab) Stream Assessment Study s Trail Master Plans Other Studies
Darby-Cobbs Delaware R. Pennypack Poquessing Tookany/Tacony- Frankford Schuylkill R. Wissahickon Act 167 SW Mgmt. Plans 2004 2013 2013 2008 2014 River Conservation Plan 2005 2011 2005 2007 2004 2001 1999 Comprehensive Characterization Reports 2004 2009 2010 2005 2007 Integrated Watershed Mgmt. Plans 2004 2013 2012 2005 Stream Assessment Study 2010 2002 2007 2002 Source Water Assessment Other Studies 2003 2011
Timeline: Comprehensive Act 167 Stormwater Management Plans Darby-Cobbs Creeks Act 167 SW Mgmt. Plan (Delaware Co. Lead), 2004 Development of Philadelphia Stormwater Standards from Darby-Cobbs Ordinance, 2005 Tookany/Tacony-Frankford Act 167 Act 167 SW Mgmt. Plan, 2008 Pennypack Creek Act 167 SW Mgmt. Plan, 2013 Poquessing Creek Act 167 Act 167 SW Mgmt. Plan, 2013 Wissahickon Creek Act 167 SW Mgmt. Plan, 2014
The Watershed Stormwater Management Plans: 1. Evaluate Existing Studies/Data 2. Adjust DEM 3. Identify and Map Stormwater Problems 4. Map Streams 5. Map Obstructions 6. Collect Hydrologic Data 7. Develop Land Use Scenarios 8. GIS/Hydrologic Model Development 9. ID Stormwater Improvements 10.Develop Management Areas/Criteria 11. Develop Model SW Ordinance 12. Plan of Action
Plans Have to Account for Past Neglect 283 linear miles of streams 118 linear miles of streams 73% Piped
Sample Comprehensive Stormwater Management Plan: Wissahickon Creek Watershed
Related Documents/ Studies: An Integrated Watershed Management Plan A Comprehensive Characterization of the Water Quality, Habitat and Biology Sandy Run Act 167 Plan River Conservation Plan
Related Documents/ Studies: Floodplain Mapping Study: Sandy Run and Ambler Area Watersheds Fort Washington Area Flooding and Transportation Improvement Study A 'Special Area Management Plan Detention Basin Inventory and Retrofit Program Friends of Wissahickon Inventory
GIS Data County and municipal boundaries Road centerlines Streams Water bodies Watershed boundary Wetlands Source PennDOT, PASDA PennDOT or DVRPC PWD PWD, PAMAP Delineated from LiDAR DEM from PAMAP U.S. Fish and Wildlife Service National Wetlands Inventory (NWI), PWD High Resolution Digital Ortho PAMAP - 2008, DVRPC - 2010 Photographs Digital Elevation Model (DEM) LiDAR from PAMAP Program - 2008 Existing Land Use DVRPC - 2005 Future Land Use DVPRC, CSC Impervious Surface Areas PWD Hydrologic Soil Groups NRCS, PWD Geology USGS, PWD Obstructions PWD, CSC, FEMA, Municipalities Floodplains (FEMA Q3) FEMA
LiDAR data from PAMAP do not have stream break lines for small tributaries. This is needed for hydraulic modeling. Contractor (BAE) hired to add break lines for areas where hydraulic modeling and flood mapping is funded. (Ambler area at this time)
Municipal Participation Data Collection Forms
Problems in the Watershed Floodplain encroachment Undersized storm drains Undersized stream channels Erosion/Sedimentation Water Quality/Pollution Existing Ordinances Others????
Flooding
Undersized or Blocked Storm Drains
Erosion / Sedimentation Problem Area
Water Quality Problem Area
Existing detention basins were ID d from aerial photography
Data was collected on the dimensions and outlet structures
Volumes were determined by overlaying LiDAR Contours on digital aerials and Stage- Storage- Discharge data was incorporated into the hydrologic model.
FEMA FIS data was collected and the floodplains utilized to ID problem areas, inundated structures, loss, etc.
Structures within Wissahickon Watershed Floodplains Municipality Building Footprints in Floodplain 100 Year 500 Year Abington 303 354 Ambler 90 91 Cheltenham 0 0 Horsham 0 0 Lansdale 16 32 Lower Gwynedd 104 124 Montgomery 6 6 North Wales 5 66 Philadelphia 5 16 Springfield 234 430 Upper Dublin 92 209 Upper Gwynedd 59 74 Upper Moreland 0 0 Whitemarsh 27 96 Whitpain 29 48 Worcester 0 0 Total 941 1546
Stormwater Problems Flood Damage Flood Insurance Payments: January 1978 March 2010 Total paid claims = 610 Total payments = $26.2 Million Flood Insurance Data provided by FEMA. Total claims payments do not represent all flood damage. 27
Obstructions
Obstruction Inventory PWD field surveyed over 700 bridges, culverts, and dams in the watershed in 2005-2006. Half of these were determined significant obstructions to flow and resurveyed in 2012-2013. From the field measurements, obstruction capacities were determined and compared to flood frequencies. Bridge Culvert Dam Scour also reported
Obstructions Rose Valley Creek Tannery Run Stuart Farm Creek
Obstructions
GIS was used to overlay land use and hydrologic soil group for each subbasin to generate CN Land Use Hydrologic Soil Group 32
Curve Number Distribution for Wissahickon Subbasins CN >85 CN 80-85 CN 75-80 CN 70-75 CN <70 Approximately 25 % of the watershed is covered by impervious surfaces such as roofs, parking lots and roads. Curve numbers in this area to be evaluated further. 33
Trend Green Residential Trend Future land use based on population projections, no site-specific BMPs. Green Future land use based on population projections and cluster housing, no site-specific BMPs. Future Based on the Green land use projections and includes additional adjustments for storage from new or retrofitted detention basins, infiltration facilities, and riparian buffers. Non-Residential
Existing Detention Storage Summed for each subbasin and added to the potential storage. The Curve number was then be adjusted. 35
Hydrologic Model HEC-HMS model Inputs based on: - 2008 LiDAR from PAMAP - 2005 Land use from DVRPC - Soils data from NRCS, PWD - Stream and x-sect. data from PWD - 2008 Ortho imagery from PASDA - Storm Sewer Shed data from PWD ArcHydro and HEC-GeoHMS used to prepare input for HEC-HMS model 137 subbasins delineated Average Drainage Area = 0.46 square miles 36
Model Calibration The model was tested for multiple rainfall events and calibrated against observed flow data at stream gages. -Fort Washington -Philadelphia Design rainfall events were based on NOAA Atlas 14 precipitation frequency data. Philadelphia Gage 64 mi 2 Fort Washington Gage 40.8 mi 2 The GIS data was exported to the HEC-HMS hydrologic model 37
Actual Storms - Storm Direction Influenced Hydrographs
Model Calibration Continuous (measured every 15 minutes) streamflow data is available at both USGS gage stations. Precipitation from several runoff-producing events will be run through the hydrologic model. The model will be calibrated so that it produces flows that are consistent with those measured by the USGS gages.
Flow (cfs) 18000 16000 14000 12000 10000 8000 Hyetograph/Hydrograph Mouth Ft. Washington Gage 18 Gage 19 Gage 21 Wings Field (1-hr) C1648 C5430 C6611 C3510 AP069 0.00 0.50 1.00 1.50 2.00 2.50 3.00 Rainfall Depth (inches) 6000 3.50 4000 4.00 2000 4.50 0 8/2/09 3:00 AM 8/2/09 6:00 AM 8/2/09 9:00 AM 8/2/09 12:00 PM 8/2/09 3:00 PM 8/2/09 6:00 PM 8/2/09 9:00 PM 8/3/09 12:00 AM 8/3/09 3:00 AM Date
Events were calibrated for both lag and peak at several points of interest (POIs). Event Lag Time to Ft. Washington Gage (hrs) Main Stem Sandy Run Peak Flow At Ft. Washington (approx cfs) Lag Time to Gage at Mouth (hrs) Peak Flow At Mouth (approx cfs) Sep-04 3.5 11000 7 15200 Jun-06 4.25 6500 8.25 6800 Oct-09 3.75 1.75 3800 8 3200 Aug-09 7 1.15 6000 10.25 6000 May-09 3 2.5 2400 7 2000 Jun-09 2.25 4800 7 4600 41
Model Calibration The calibrated model output was be compared with peak flow estimates calculated using several widely accepted methods.
Peak and timing of hydrographs were analyzed at each POI 43
Determine Management District
Assign Overall Management Districts District A = standard detention District B = alternate storm district District C = conditional direct discharge 45
Hydraulic Model HEC-RAS Ambler portion of the watershed. Rose Valley Creek Sandy Run Watershed Tannery Run Stuart Farm Creek Sandy Run Watershed 46
Model Ordinance: - ERSAM - SWM Site Plan Requirments - Groundwater Recharge - Water Volume Control - Channel Protection - Flood Control
Final Products: -Inventory of detention basins with proposed retrofits (Wm Penn) - Inventory of problem areas with proposed solutions (Wm Penn) - Final report - Model Stormwater Mgmt. Ordinance - FEMA flood flows - Basis for flood control projects - Plan of action to implement all various previously prepared programs
Questions????