Climate and Land Use Consequences to 100-Year Flooding Presented by: Ann Scholz, PE, CPSWQ Grad Student, University of New Hampshire Robert Roseen & Thomas Ballestero, UNH Stormwater Center Michael Simpson, Antioch Universtity New England Colin Lawson, Trout Unlimited Eastern Conservation Fay Rubin & Cameron Wake, Institute for the Study of Earth, Oceans and Space, UNH 2011 World Environmental & Water Resources Congress Palm Springs, California May 23, 2011
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 2
Lamprey River Watershed 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
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 6
Hydrology Overview Standard Hydrologic Grid Hydrologic Rainfall Analysis Project HEC-GeoHMS (ArcHydroTools) to process DEM Delineate Watershed and Sub-watershed GIS Preprocessed Spatial Hydrology Data Base DEM Reconditioning Runoff Parameters Stream Network HEC-HMS Input File 7
Watershed Hydrologic Analysis W6730 W7060 W6510 Subbasin Area (mi2) W6510 32.2 W8600 19.0 W11900 16.0 W10910 6.5 W8380 12.3 W11020 6.1 W6730 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 8
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 W6730 65.4 W7060 63.9 W7920 67.7 W10250 66.0 W8590 71.0 W6510 W6730 W7060 W7920 W8600 W8380 W8590 W11020 W11900 W10910 W10250 9
LID Buildout Scenarios Commercial Zoning One Acre Residential Runoff Curve Number Reduction Method from : 1. McCuen, R. and M. D. E. (1983). Changes in Runoff Curve Number Method; 2. Maryland Department of Environment (2008). Maryland Stormwater Design Manual, Supplement No. 1. 10
2050 CN Values Moonlight Brook, Newmarket Current Conditions, CN = 66.8 Conventional Build-Out, CN = 78.0 LID Build-Out CN = 69.5 11
Regional Curve Number 12
Hydrologic Model Scenarios Project Models Rainfall Rates and Global Change Model Scenario Climate Period Climate Period Land Use Rainfall Atlas 2035-2069 2070-2099 Conditions TP-40 NRCC NRCC Regional Model 6.3 in/hr 8.5 in/hr 8.5 in/hr X in/hr Current 2005 2005 Build-out 2050 2085 LID/Build-out 2050 2085 13
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 14
HEC-GeoRAS Hydraulic Analysis 15
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% 16
Hydraulics Model Results for RT108
Hydraulics Model Results for RT108 45 40 River = Beaudette Brook Reach = DS RT108 FP.06.07.06 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 Legend WS SCS 100-YR WS 04-07 WS 03-10 Ground Bank Sta tion (ft) Elevat 35 30 25 20-1000 0 1000 2000 3000 4000 Station (ft) 18
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 19
Watershed Buildout 20
Flood Flows 21
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 22
Funding Funding is provided by the Cooperative Institute for Coastal and Estuarine Environmental Technology (CICEET) whose mission is to support the scientific development of innovative technologies for understanding and reversing the impacts of coastal and estuarine contamination and degradation.
Thank you for your time. Questions?