Assessing the Risk of 100-year Freshwater Floods in the Lamprey - - PowerPoint PPT Presentation

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Assessing the Risk of 100-year Freshwater Floods in the Lamprey - - PowerPoint PPT Presentation

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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

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Assessing the Risk of 100-year Freshwater Floods in the Lamprey River Watershed of New Hampshire Resulting from Changes in Climate and Land Use

Newmarket, NH April 2007

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

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Outline

  • Project Objectives
  • Importance of Research
  • Lamprey River/Watershed
  • Methodology
  • Research Status

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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

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15 Highest Events –

Daily Discharges on Lamprey River near Newmarket

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

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

Source: http://waterdata.usgs.gov/nwis

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FEMA Requirements for Redelineation

  • Hydrologic Analysis:
  • Bulletin 17B for gaged streams

Effective Model – 1935 through 1987 Q100 = 7,300 cfs

  • Criteria for revised hydrologic analysis

Statistically Significance (68-percent confidence interval) L0.01,0.68 = 6,886 cfs H0.01,0.68 = 7,834 cfs 75 yr record – 1935 - 2009 Q100 = 9,411 cfs Statistically Significant

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Change to Base Flood Elevation and Spatial Extents

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Lamprey River Watershed

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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

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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

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Hydrology Overview

GIS Preprocessed Spatial Hydrology Data Base

HEC‐GeoHMS (ArcHydro Tools) to process DEM Standard Hydrologic Grid Hydrologic Rainfall Analysis Project Delineate Watershed and Sub‐watershed DEM Reconditioning Stream Network HEC‐HMS Input File Runoff Parameters 10

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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 W8590 0.9 Total 211.7

W7060 W1380 W8590 W10910 W8380 W11900 W6510 W7920 W10250

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W8600 W11020

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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

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W7060 W1380 W8590 W10910 W8380 W11900 W6510 W7920 W10250 W8600 W11020

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UNH Hydrology Model

  • Rainfall
  • 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.

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  • Calibration:
  • April 2007 – 7,590 cfs, Precipitation – 7.65 in
  • March 2010 – 6,550 cfs, Precipitation – 7.02 in
  • Optimization parameters:
  • Manning’s ‘n’
  • Lag Time
  • Simulated for
  • Time to peak
  • Runoff volume
  • Peak flow

Calibrating the Watershed

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Calibrating the Watershed

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Calibrating the Watershed

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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. Q100, TP-40 = 7,580 cfs vs. Q100, FIS = 7,300 cfs

  • Results of calibrated model run for current land use (2005) using

NRCC Atlas rainfall. Q100, CA = 10,649 cfs

  • 68-percent confidence interval of gaging station estimate for data

from 1935-2009, Q100, LP3 = 9,411 cfs L0.01,0.68 = 8,862 cfs H0.01,0.68 = 10,040 cfs

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Calibrating the Watershed

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Hydrologic Studies

Project Models

Land Use Conditions Rainfall Rates and Global Change Model Scenario 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 A1F1 (HI) - Continuation of growth TP-40 – Technical Paper 40 B1 - Stabilizing CO2 concentrations

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Hydraulic Overview

GIS Preprocessed Spatial Hydrology Data Base

HEC‐ GeoRAS (ArcView ) Create Stream Stationing and Reaches Create Stream Cross Sections Extract Elevation Data HEC‐RAS Input File RAS Mapping 20

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Cross Section A10

East 265, 283 Wadleigh Falls Road Lee, NH

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FEMA Library Historic Data and Development of Floodplain Hydraulics Model

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Hydraulics Model – Cross Sections

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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
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Hydraulics Model – Structural Data

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Summary of Bridge Structure Source for the Lamprey River Community Station Road Name Data Source Raymond 181300 Dudley Road Electronic WSP2 files from Roald Haestad, Inc. March 1993 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 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) FEMA FIS Backup Data Longmarsh Brook 4182 Bedard Road Longmarsh Brook 1703 Longmarsh Road Longmarsh Brook 275 Tote Road

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Hydraulics Model – Dam and In-line Structural Data

25 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
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HEC-GeoRAS Hydraulic Analysis

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Hydraulics Model

  • Boundary Conditions
  • FIS backup data (effective model flows)
  • Rating Curve for Macallen Dam
  • Normal Depth for Hamil Brook

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Hydraulics Model – Diverted Flow

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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%

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

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Hydraulics Model – Results for RT108

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April 2007 WSE = 34.41 March 2010 WSE =33.58

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NRCC 100-YR WSE = 35.83 FIS WSE = 33.0 Observed WSE: April 2007 – 34.1 March 2010 – 33.3

Hydraulics Model – Results for RT108

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Hydraulics Model – Results for upstream of Mill Street, Epping

April 2007 WSE = 112.01 SCS 100-YR WSE = 114.12 FIS WSE = 110.6 Observed WSE: April 2007 – 113.0

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Hydraulics Model – Rating curve comparisons at USGS gage

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Hydraulics Model – General Profile Plot

20 40 60 80 100 120 140 160 180 200 220 20000 40000 60000 80000 100000 120000 140000 160000 180000 Elevation (ft) Reach Length (ft)

Lamprey River EGL Profile Plot

HEC-RAS FIS

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Hydraulics Model – General Profile Plot

25 27 29 31 33 35 5000 6000 7000 8000 9000 10000 Elevation (ft) Reach Length (ft)

Longmarsh Brook to Hamil Brook Profile Plot

HEC-RAS FIS

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Watershed Buildout

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LID Buildout

36 Commercial Zoning

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LID Buildout

37 One Acre Residential

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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

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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

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Thank you for your time. Questions?