May 1997 {",--< "<~/-' -------_....... _------------------ Southern Massachusetts Hurricane Evacuation Study Technical Data Report COMMONWEALTH OF MASSACHUSETTS NANTUCKET SOUND us Army Corps of Engineers New Englarrl District REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704·0188 Public reporting burden for this collection of information is estimated 10 avera~ 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and malntalnln~ the data needed, and completing and reviewing the collectIOn of informatIOn. Send comments regarding this burden estimate or an~ other aspect 01 this COllection of information, inc uding suggestIOns for reducing this burden, to Washington Headquarters Services. Directorate for tnformation ~ralions and Reports, 1 15 Jefferson Davis Highway. Suite 1204. Arlington. VA 222 2-4302, and to the OffiCe 01 Management and Budget. Paperwork ReductiOn Project (0704-0188), Wasn,lngton, DC 20503. 1. AGENCY USE ONLY (Leave blank) 12. REPORT DATE 3 REPORT TYPE AND DATES COVERED 1 . May 1997 PL 93·288. PL 86-645 1997 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Southern Massachusetts Hurricane Evacuation Study Technical Data Report 6. AUTHOR(S) Department of the Army Corps of Engineers. New England Division Waltham. MA 02254-9149 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(E:;) 8. PERFORMING ORGANIZATION US Army Corps of Engineers REPORT NUMBER New England Division Planning Directorate 424 Trapelo Road W.lth.m. MA 02254-9149 9. SPONSORINGIMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORINGIMONITORING Federal Emergency Management Agency, Region I AGENCY REPORT NUMBER Room 462. l.W. McCormack Post Office and Court House Boston. MA 02109 11. SUPPLEMENTARY NOTES Main Report of the Southern Massachusetts Hurricane Evacuation Study, May 1997 120. DISTRIBUTION AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Approved for public release; distribution unlimited 13. ABSTRACT (Maximum 200 words) This report and its companion atlases were completed as part of the Hurricane Evacuation Study program cosponsored by the Federal Emergency Management Agency and the U.S. Army Corps of Engineers. The purpose of the study is to provide the Massachusetts Emergency Management Agency and coastal communities in Southern Massachusetts with realistic data quantifying the major factors involved in hurricane evacuation decision-making. To accomplish this. the study provides information on the extent and severity of potential flooding from hurricanes, the associated vulnerable population. capacities 0 existing public shelters and estimated sheltering requirements, and evacuation roadway clearance times. The report also provides guidance on how this information can be used with National Hurricane Center advisories for hurricane evacuation decision-making. 14. SUBJECT TERMS 15. NUMBER OF PAGES Massachusetts. Emergency Management, Hurricanes 260 16. PRICE CODE. 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF OF REPORT OF THIS PAGE OF ABSTRACT ABSTRACT unclassified unclassified unclassified ~,\"ndord,.:.orm.il9~:l":WV. 2-89) (e"') re~nbedbyANSt td.2 ,18 DeSigned uSing Pelforrn Pro, WHSlDIOR, Oct 94 Executive Summary AUTHORITY At the request of the Governor of Massachusetts, the Federal Emergency Management Agency (FEMA) and the US Army Corps of Engineers cooperatively sponsored and conducted the Southern Massachusetts Hurricane Evacuation Study. The study was completed with direct assistance provided by the National Oceanic and Atmospheric Administration (NOAA) and the Massachusetts Emergency Management Agency. Funding was provided by FEMA under the Disaster Relief Act of 1974 and by the Corps of Engineers under its Flood Plain Management Services program authorized in Section 206 of the Flood Control Act of 1960. SCOPE AND PURPOSE The purpose of this study was to provide the Massachusetts Emergency Management Agency and coastal communities in southern Massachusetts, including Cape Cod and the Islands, with data quantifying the major factors involved in hurricane evacuation decision-making. The results of this study are not intended to replace existing hurricane preparedness plans but rather to provide state-of-the-art information that can be used to update or revise current plans. The study provides information on the extent and severity of potential flooding from hurricanes, the associated vulnerable population, capacities of existing public shelters and estimated sheltering requirements, and evacuation roadway clearance times. The report also provides guidance on how this information can be used -with National Hurricane Center advisories for hurricane evacuation decision­ making. Products developed from the study include the Southern Massachusetts Hurricane Evacuation Study. Technical Data Report, and two companion atlases. The first atlas, the Inundation Map Atlas, shows the areas within communities most vulnerable to flooding from hurricanes. In partnership with local officials, a second atlas, the Evacuation Map Atlas, was developed to identifY land areas ( evacuation zones) vulnerable to hurricane surge which should be considered for evacuation prior to a hurricane's landfall. The extent ofland area included within evacuation zones is based on the surge inundation areas depicted in the Inundation Map Atlas. Evacuation zones encompass all land areas shown to be potentially inundated, as well as areas ofland that would be isolated by surrounding ES-I surge. The Evacuation Map Atlas also gives the locations of public shelters, medicaVinstitutional facilities, and mobile home/trailer parks. HAZARDS ANALYSIS The purpose of the Hazards Analysis was to develop accurate estimates of the potential surge inundation areas resulting from hurricanes. Because this study focuses on protection of the vulnerable population, the study used "worst case" hurricane surge estimates provided by the National Hurricane Center's Sea, Lake, and Overland Surges from Hurricanes (SLOSH) computer model. The SLOSH model simulated several hundred hypothetical hurricanes of varying intensities, forward speeds, and track directions in order to calculate the potential hurricane surge which may be experience<;i in coastal communities in southern Massachusetts. Simulations were performed for hurricanes of SaffirlSimpson scale intensity categories 1_4' (see Table 1.4 in the report), with forward speeds ranging from 20 to 60 miles per hour, and the storm track directions most likely to affect southern Massachusetts. The study discusses the difficulties offorecasting the precise tracks of hurricanes, and reports that the average error in the National Weather Service 12 hour track forecast is approximately 60 miles. Because of the uncertainties in hurricane track forecasting, the study assumed that all southern Massachusetts locations are equally vulnerable to each hurricane forecasted to affect the region. Therefore, worst case surge inundation areas provided in the Inundation Map Atlas were developed based on a composite of the critical hurricane tracks and approach directions for all locations. The three surge inundation areas delineated in the Inundation Map Atlas were categorized based on the forward speeds and intensities of the hurricanes modeled using the SLOSH model. These hurricane parameters can be more confidently forecasted by the National Weather Service. Categorized SLOSH model results are shown on Plate iii ofthe study's Inundation Map Atlas. 'Category 5 hurricanes were omitted from the analysis based upon the National Hurricane Center's recommendation that the cooler ocean waters along the northeast coast of the United States are not capable of sustaining hurricanes of this intensity. ES-2 VULNERABILITY ANALYSIS Approximately one-tenth of Massachusetts' six million residents are located in the 37 study communities (I 990 Census). In general, surge vulnerable areas in southern Massachusetts are densely developed with many businesses, multifamily housing units, and beach front and near shore homes. In the 37 southern Massachusetts coastal communities included in this study, there are approximately 205,000 residents potentially vulnerable to hurricane surge from a "weak hurricane scenario" and more than 288,000 residents vulnerable from a "strong hurricane scenario" (see Tables 3.1 and 3.2 in the report). Communities in which more than 25% ofthe summer population were found to live in areas vulnerable to "weak" hurricane surge flooding include: Bourne, Chatham, Dennis, Falmouth, Mashpee, Orleans, and Wellfleet in Barnstable County; Fairhaven and Swansea in Bristol County; Gosnold in Dukes County; Nantucket; and Marion, Mattapoisett, and Wareham in Plymouth County. In addition to the above communities, the following communities were found to have more than 25% of the summer population living in areas vulnerable to "severe" hurricane surge flooding: Eastham, Harwich, Provincetown, and Yarmouth in Barnstable County; and Edgartown and Oak Bluffs in Dukes County. The summer population includes permanent residents and those who rent houses for anywhere from one week to the entire summer, but excludes day trippers. BEHA VIORAL ANALYSIS The study recognized that not all residents within evacuation zones will respond to officials' recommendations to evacuate their homes. Because varying individual response impacts the evacuation process, a behavioral analysis was conducted to provide an estimate of how the majority of the affected public can be expected to respond