Assessing the Risk of 100-year Freshwater Floods in the Lamprey River Watershed of New Hampshire Resulting from Changes in Climate and Land Use Presented by: Ann Scholz, PE, CPSWQ Advisor: Dr. Robert Roseen, PE, D.WRE Funding: The Cooperative Institute for Coastal and Estuarine Environmental Technology Principal Investigator: Cameron Wake Technical Support : Robert Roseen, PE, PhD, Thomas Ballestero, PE, PhD, Michael Simpson Newmarket, NH April 2007
Outline Project Objectives Importance of Research Lamprey River/Watershed Methodology Research Status 2
Project Objectives Construct a current hydrologic and hydraulic model for the watershed and river respectively Improve the existing information regarding base flood elevations and flood risk areas Assess the effect of future development and increased precipitation due to climate change Present land use management strategies to mitigate runoff volumes 3
15 Highest Events Daily Discharges on Lamprey River near Newmarket Rank Date Discharge (cfs) 1 16 May 06 8400 15 May 06 7600 2 18 Apr 07 7590 17 Apr 07 7410 3 7 Apr 87 7360 8 Apr 87 5920 6 Apr 87 5460 4 16 Mar 10 6550 17 Mar 10 5610 15 Mar 10 4810 5 22 Oct 96 6310 23 Oct 96 6150 6 17 May 06 6240 7 20 Mar 36 5270 21 Mar 36 4690 8 1 Apr 10 5240 31 Mar 10 4600 9 19 Apr 07 4830 10 27 Feb 10 4640 11 15 Mar 77 4620 12 3 Apr 04 4550 13 16 Jun 98 4500 15 Jun 98 4400 14 21 Mar 83 4310 15 6 Apr 60 4270 Of 15 largest events since 1934: 11 have occurred in last 25 years 10 have occurred in last 15 years 7 have occurred in last 5 years Source: http://waterdata.usgs.gov/nwis 4
FEMA Requirements for Redelineation Hydrologic Analysis: o Bulletin 17B for gaged streams Effective Model 1935 through 1987 Q 100 = 7,300 cfs o Criteria for revised hydrologic analysis Statistically Significance (68-percent confidence interval) L 0.01,0.68 = 6,886 cfs H 0.01,0.68 = 7,834 cfs 75 yr record 1935-2009 Q 100 = 9,411 cfs Statistically Significant 5
Change to Base Flood Elevation and Spatial Extents 6
Lamprey River Watershed 7
Lamprey River Studies Summary of Town Studies Community Town FIS Date Study performed by Completed Raymond October 15, 1981 SCS September 1979 April 15, 1992 Rivers Engineering Corp. October 1989 May 2, 1995 Roald Haestad, Inc. March 1993 Epping October 15, 1981 SCS September 1979 Lee No published study available Durham May 3, 1990 SCS September 1987 August 23, 2001 USGS April 1998 Newmarket May 2, 1991 USGS August 1989 8
GIS Data Assembly Terrain Digital Elevation Model (DEM) Watershed(s) Hydrologic Unit Code (HUC) Transportation data and water features Digital Line Graph (DLG) Stream Networks River Reach Files (RF)/National Hydrography Dataset (NHD) Streamflow Gage Data Locations Latitude/Longitude Aerial Background Digital Orthophoto Quarter Quads (DOQQ) Soil type data Soil Surveys Geographic Data Base (SSURGO) State Soil Geographic Data Base (STATSGO) Land Use Cover USGS Land Use Land Cover (LULC) State/Municipal GIS 9
Hydrology Overview Standard Hydrologic Grid Hydrologic Rainfall Analysis Project HEC GeoHMS (ArcHydro Tools) to process DEM Delineate Watershed and Sub watershed GIS Preprocessed Spatial Hydrology Data Base DEM Reconditioning Runoff Parameters Stream Network HEC HMS Input File 10
Watershed Hydrologic Analysis W1380 W7060 W6510 Subbasin Area (mi2) W6510 32.2 W8600 19.0 W11900 16.0 W10910 6.5 W8380 12.3 W11020 6.1 W1380 58.3 W7060 33.9 W7920 4.5 W10250 21.7 W8590 0.9 Total 211.7 W7920 W8600 W8380 W11020 W8590 W11900 W10910 W10250 11
Land Use Within the Watershed Subbasin CN W6510 62.5 W8600 63.0 W11900 64.2 W10910 61.2 W8380 63.5 W11020 62.5 W1380 65.4 W7060 63.9 W7920 67.7 W10250 66.0 W8590 71.0 W6510 W1380 W7060 W7920 W8600 W8380 W8590 W11020 W11900 W10910 W10250 12
UNH Hydrology Model Rainfall o Depth-duration-frequency TP-40 Rainfall Frequency Atlas of the United States is being used for effective conditions Northeast Regional Climate Center Atlas for Extreme Precipitation. FEMA guidelines for redelineation indicate the need to use current depth duration frequency data. 13
Calibrating the Watershed Calibration: o April 2007 7,590 cfs, Precipitation 7.65 in o March 2010 6,550 cfs, Precipitation 7.02 in Optimization parameters: o Manning s n o Lag Time Simulated for o Time to peak o Runoff volume o Peak flow 14
Calibrating the Watershed 15
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Calibrating the Watershed 17
Calibrating the Watershed Hydrology Model Calculated flood flow for the gaged 183 sq.mi. watershed Results of calibrated model run for current land use (2005) using TP-40 rainfall. Q 100, TP-40 = 7,580 cfs vs. Q 100, FIS = 7,300 cfs Results of calibrated model run for current land use (2005) using NRCC Atlas rainfall. Q 100, CA = 10,649 cfs 68-percent confidence interval of gaging station estimate for data from 1935-2009, Q 100, LP3 = 9,411 cfs L 0.01,0.68 = 8,862 cfs H 0.01,0.68 = 10,040 cfs 18
Hydrologic Studies Project Models Rainfall Rates and Global Change Model Scenario Land Use Conditions Effective Updated Climate Period 2006-2030 Climate Period 2031-2085 TP-40 NRCC NRCC A1F1 (HI) B1 (LO) Current (2005) X X Build-out X X X LID/Build-out X X X NRCC Northeast Regional Climate Center TP-40 Technical Paper 40 A1F1 (HI) - Continuation of growth B1 - Stabilizing CO 2 concentrations 19
Hydraulic Overview HEC GeoRAS (ArcView ) Create Stream Stationing and Reaches GIS Preprocessed Spatial Hydrology Data Base Create Stream Cross Sections Extract Elevation Data HEC RAS Input File RAS Mapping 20
Cross Section A10 East 265, 283 Wadleigh Falls Road Lee, NH 2
FEMA Library Historic Data and Development of Floodplain Hydraulics Model 22
Hydraulics Model Cross Sections Summary of Cross Section Data Source Source Number FEMA FIS Backup Data 111 Duplicates 19 Surveyed 12 NHDOT/Consultants 34 GIS 44 Total 220 FIS sections were duplicated as needed to provide immediate sections up and downstream of bridges No backup data available for Lee Projects included additional sections supplementing FIS sections Improved modeling in RT108 corridor and tributaries 23
Hydraulics Model Structural Data Summary of Bridge Structure Source for the Lamprey River Community Station Road Name Data Source Raymond 181300 Dudley Road 180964 Raymond Road (RT 27) 167900 Langford Road 160746 Main Street 155060 Epping Street 154106 B&M Railroad 147643 Freetown Road (RT 107) 141372 Prescott Road Epping 136759 State Route 101 Electronic WSP2 files from Roald Haestad, Inc. March 1993 127937 Epping Road (RT 27) Electronic HEC RAS files from NHDOT, 2010 123964 Blake Road 107459 Main Street (Plummer) As built drawings from NHDOT, dates vary 106269 Mill Street 105560 Calef Hwy (RT 125) Electronic HEC RAS files from NHDOT, 2000 88171 Hedding Road (RT 87) WSPRO print out and As built from NHDOT, 2000 Lee 61457 Wadleigh Falls Road 35683 Lee Hook Road As built drawings from NHDOT, dates vary Durham 20082 Wiswall Road Electronic HEC RAS files from CLD Consulting, 2009 16028 Packer's Falls Road Newmarket 1602 RT 108 FEMA FIS Backup Data Summary of Bridge Structure Source for the RT108 Corridor Watercourse Station Road Name Data Source Floodplain 71 Newmarket Road (RT 108) Survey drawings from NHDOT, 2010 Hamil Brook 1040 Newmarket Road (RT 108) Longmarsh Brook 4182 Bedard Road Longmarsh Brook 1703 Longmarsh Road FEMA FIS Backup Data Longmarsh Brook 275 Tote Road 24
Hydraulics Model Dam and In-line Structural Data Summary of In line Structure Source for the Lamprey River Community Station Road Name Data Source Epping 127265 Bunker Pond Dam Electronic HEC RAS files from NHDOT Lee 61266 Wadleigh Falls Dam Land Records Durham 19859 Wiswall Dam Electronic HEC RAS files from CLD Consulting Engineers Newmarket 1286 Coffee Sluice Newmarket 1164 Macallen Dam Electronic HEC RAS files from Wright Pierce NHDES Dam Management studying removal of Bunker Pond dam Wiswall bridge has been replaced and downstream dam replacement in near future Macallen Dam recently inspected per NHDES request Spillway dimensions and layout, elevation field verified 25
HEC-GeoRAS Hydraulic Analysis 26
Hydraulics Model Boundary Conditions o FIS backup data (effective model flows) o Rating Curve for Macallen Dam o Normal Depth for Hamil Brook 27
Hydraulics Model Diverted Flow Effective Model Assumed 20-percent of flood flow bypassed to the Oyster River watershed HEC-RAS Junction at Lamprey River and RT 108 floodplain corridor Reach River Sta Profile W.S. Elev E.G. Elev Q Total Downstream (ft) (ft) (cfs) EGL Diff. USaltRT101 8998 SCS 100 YR 36.72 36.89 10,649 0.01 USaltRT101 8998 7 Apr 35.2 35.33 8,332 0.01 USaltRT101 8998 10 Mar 34.36 34.48 7,481 0.02 Junction: RT108 FP Optim. % Bypass DS RT108 FP 8890 SCS 100 YR 36.58 36.84 9,158 86.0% DS RT108 FP 8890 7 Apr 35.06 35.28 7,440 89.3% DS RT108 FP 8890 10 Mar 34.27 34.46 6,361 85.0% OR_Bypass 6377 SCS 100 YR 36.82 36.83 1,491 14.0% OR_Bypass 6377 7 Apr 35.28 35.29 956 11.5% OR_Bypass 6377 10 Mar 34.43 34.44 1,125 15.0% 28
Hydraulics Model Results for RT108
Hydraulics Model Results for RT108 NRCC 100-YR WSE = 35.83 April 2007 WSE = 34.41 March 2010 WSE =33.58 FIS WSE = 33.0 Observed WSE: April 2007 34.1 March 2010 33.3 30
Hydraulics Model Results for upstream of Mill Street, Epping SCS 100-YR WSE = 114.12 April 2007 WSE = 112.01 FIS WSE = 110.6 Observed WSE: April 2007 113.0 31
Hydraulics Model Rating curve comparisons at USGS gage 32
Hydraulics Model General Profile Plot 220 Lamprey River EGL Profile Plot 200 180 160 140 Elevation (ft) 120 100 80 60 40 20 0 20000 40000 60000 80000 100000 120000 140000 160000 180000 Reach Length (ft) HEC-RAS FIS 33
Hydraulics Model General Profile Plot Longmarsh Brook to Hamil Brook Profile Plot 35 33 Elevation (ft) 31 29 27 25 5000 6000 7000 8000 9000 10000 Reach Length (ft) HEC-RAS FIS 34
Watershed Buildout 35
LID Buildout Commercial Zoning 36
LID Buildout One Acre Residential 37
Research Status Model buildout scenarios for 2050 and 2085 with traditional and low impact design features Run hydraulic model with flood flows Map spatial extent of flood areas 38
Acknowledgments Robert Roseen, Director, UNH Stormwater Center Thomas Ballestero, Department of Civil Engineering, UNH Cameron Wake, Institute for the Study of Earth, Oceans and Space, UNH Steve Miller, Great Bay National Estuarine Research Reserve Kathy Mills, Great Bay National Estuarine Research Reserve Fay Rubin, Institute for the Study of Earth, Oceans and Space, UNH Michael Simpson, Antioch University New England Lisa Townson and Julia Peterson, UNH Cooperative Extension Cliff Sinnott, Rockingham Planning Commission 39
Thank you for your time. Questions?