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 Discharge Rank Date (cfs) 1 16 ‐ May ‐ 06 8400 15 ‐ May ‐ 06 7600 2 18 ‐ Apr ‐ 07 7590 17 ‐ Apr ‐ 07 7410 3 7 ‐ Apr ‐ 87 7360 Of 15 largest events since 1934: 8 ‐ Apr ‐ 87 5920 6 ‐ Apr ‐ 87 5460 11 have occurred in last 25 years 4 16 ‐ Mar ‐ 10 6550 10 have occurred in last 15 years 17 ‐ Mar ‐ 10 5610 15 ‐ Mar ‐ 10 4810 7 have occurred in last 5 years 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 Source: 15 ‐ Jun ‐ 98 4400 http://waterdata.usgs.gov/nwis 14 21 ‐ Mar ‐ 83 4310 4 15 6 ‐ Apr ‐ 60 4270
FEMA Requirements for Redelineation • Hydrologic Analysis: Bulletin 17B for gaged streams o Effective Model – 1935 through 1987 Q 100 = 7,300 cfs Criteria for revised hydrologic analysis o � 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
7 Lamprey River Watershed
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 Delineate (ArcHydro Tools) Watershed and to process DEM Sub ‐ watershed DEM Reconditioning HEC ‐ HMS Input File GIS Runoff Preprocessed Parameters Spatial Hydrology Data Base Stream Network 10
Watershed Hydrologic Analysis 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 W1380 W8590 0.9 Total 211.7 W7060 W6510 W7920 W8600 W8380 W8590 W11020 W11900 W10250 W10910 11
Land Use Within the Watershed Subbasin CN W6510 62.5 W1380 W8600 63.0 W11900 64.2 W10910 61.2 W8380 63.5 W11020 62.5 W6510 W1380 65.4 W7060 63.9 W7920 67.7 W10250 66.0 W7060 W8590 71.0 W7920 W8600 W8380 W8590 W11020 W11900 W10250 W10910 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 re- delineation indicate the need to use current depth duration frequency data. 13
Calibrating the Watershed • Calibration: April 2007 – 7,590 cfs, Precipitation – 7.65 in o March 2010 – 6,550 cfs, Precipitation – 7.02 in o • Optimization parameters: Manning’s ‘n’ o Lag Time o • Simulated for Time to peak o Runoff volume o Peak flow o 14
15 Calibrating the Watershed
1 6
17 Calibrating the Watershed
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 Effective Updated Climate Period 2006-2030 Climate Period 2031-2085 Conditions 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 A1F1 (HI) - Continuation of growth TP-40 – Technical Paper 40 B1 - Stabilizing CO 2 concentrations 19
Hydraulic Overview HEC ‐ Create Stream GeoRAS Stationing and (ArcView ) Reaches Create Stream HEC ‐ RAS Cross Sections Input File GIS Preprocessed Extract Spatial Hydrology Elevation Data Data Base 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 Electronic WSP2 files from Roald Haestad, Inc. 155060 Epping Street March 1993 154106 B&M Railroad 147643 Freetown Road (RT 107) 141372 Prescott Road Epping 136759 State Route 101 127937 Epping Road (RT 27) Electronic HEC ‐ RAS files from NHDOT, 2010 123964 Blake Road As ‐ built drawings from NHDOT, dates vary 107459 Main Street (Plummer) 106269 Mill Street Electronic HEC ‐ RAS files from NHDOT, 2000 105560 Calef Hwy (RT 125) 88171 Hedding Road (RT 87) WSPRO print out and As ‐ built from NHDOT, 2000 Lee 61457 Wadleigh Falls Road As ‐ built drawings from NHDOT, dates vary 35683 Lee Hook Road Durham 20082 Wiswall Road Electronic HEC ‐ RAS files from CLD Consulting, 2009 16028 Packer's Falls Road FEMA FIS Backup Data Newmarket 1602 RT 108 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 FEMA FIS Backup Data Longmarsh Brook 1703 Longmarsh Road 24 Longmarsh Brook 275 Tote Road
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 Electronic HEC ‐ RAS files from Wright ‐ Pierce Newmarket 1164 Macallen Dam • 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
26 HEC-GeoRAS Hydraulic Analysis
Hydraulics Model • Boundary Conditions FIS backup data (effective model flows) o Rating Curve for Macallen Dam o Normal Depth for Hamil Brook o 27
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