Flood Risk Report Concord River Watershed Middlesex and Worcester Counties, Massachusetts: Report Number 001 2/27/2013 CONCORD FLOOD RISK REPORT i This page left intentionally blank. CONCORD RIVER WATERSHED FLOOD RISK REPORT Project Area Community List Community Name Community Name Town Of Acton Town Of Tewksbury Town Of Ashland Town Of Upton Town Of Bedford Town Of Wayland Town Of Berlin Town Of Westborough Town Of Billerica Town Of Westford Town Of Bolton Town Of Weston Town Of Boxborough Town Of Boylston Town Of Carlisle Town Of Chelmsford Town Of Clinton Town Of Concord Town Of Framingham Town Of Grafton Town Of Harvard Town Of Holliston* Town Of Hopkinton Town Of Hudson Town Of Lincoln Town Of Littleton City Of Lowell City Of Marlborough Town Of Maynard Town Of Natick Town Of Northborough Town Of Sherborn Town Of Shrewsbury Town Of Southborough Town Of Stow Town Of Sudbury CONCORD RIVER WATERSHED FLOOD RISK REPORT i This page left intentionally blank. CONCORD RIVER WATERSHED FLOOD RISK REPORT Preface The Department of Homeland Security (DHS), Federal Emergency Management Agency’s (FEMA) Risk Mapping, Assessment, and Planning (Risk MAP) program provides states, tribes, and local communities with flood risk information and tools that they can use to increase their resilience to flooding and better protect their citizens. By pairing accurate floodplain maps with risk assessment tools and planning and outreach support, Risk MAP has transformed traditional flood mapping efforts into an integrated process of identifying, assessing, communicating, planning for, and mitigating flood‐related risks. This Flood Risk Report (FRR) provides non‐regulatory information to help local or tribal officials, floodplain managers, planners, emergency managers, and others better understand their flood risk, take steps to mitigate those risks, and communicate those risks to their citizens and local businesses. Because flood risk often extends beyond community limits, the FRR provides flood risk data for the entire Flood Risk Project as well as for each individual community. This also emphasizes that flood risk reduction activities may impact areas beyond jurisdictional boundaries. Flood risk is always changing, and there may be other studies, reports, or sources of information available that provide more comprehensive information. The FRR is not intended to be regulatory or the final authoritative source of all flood risk data in the project area. Rather, it should be used in conjunction with other data sources to provide a comprehensive picture of flood risk within the project area. CONCORD RIVER WATERSHED FLOOD RISK REPORT ii This page left intentionally blank. CONCORD RIVER WATERSHED FLOOD RISK REPORT Table of Contents 1 Introduction ............................................................................................................................. 1 1.1. About Flood Risk ............................................................................................................. 1 1.1.1 Calculating Flood Risk ............................................................................................. 1 1.1.2 Risk MAP Flood Risk Products ................................................................................ 1 1.2. Uses of this Report ........................................................................................................... 2 1.3. Sources of Flood Risk Assessment Data Used ................................................................. 3 1.4. Related Resources ............................................................................................................ 4 2 Flood Risk Analysis ................................................................................................................ 5 2.1. Overview .......................................................................................................................... 5 2.2. Analysis of Risk ............................................................................................................... 5 2.2.1 Changes Since Last FIRM ........................................................................................ 6 2.2.4 Areas of Mitigation Interest ...................................................................................... 9 2.3. Flood Risk Map .............................................................................................................. 18 2.4. Concord Flood Risk Project Area Summary .................................................................. 19 2.4.1 Overview ................................................................................................................. 19 2.4.2 Flood Risk Datasets ................................................................................................ 21 2.5. Communities .................................................................................................................. 24 2.5.1 City Of Lowell Summary (CID 250201) ................................................................ 24 2.5.2 City Of Marlborough Summary (CID 250203) ...................................................... 27 2.5.3 Town Of Acton Summary (CID 250176) ............................................................... 30 2.5.4 Town Of Ashland Summary (CID 250179)............................................................ 33 2.5.5 Town Of Bedford Summary (CID 255209) ............................................................ 36 2.5.6 Town Of Berlin Summary (CID 250294) ............................................................... 39 2.5.7 Town Of Billerica Summary (CID 250183) ........................................................... 42 2.5.8 Town Of Bolton Summary (CID 250296) .............................................................. 45 2.5.9 Town Of Boxborough Summary (CID 250184) ..................................................... 48 2.5.10 Town Of Boylston Summary (CID 250297) .......................................................... 51 2.5.11 Town Of Carlisle Summary (CID 250187) ............................................................ 54 2.5.12 Town Of Chelmsford Summary (CID 250188) ...................................................... 57 2.5.13 Town Of Clinton Summary (CID 250300) ............................................................. 60 2.5.14 Town Of Concord Summary (CID 250189) ........................................................... 63 2.5.15 Town Of Framingham Summary (CID 250193) .................................................... 66 CONCORD RIVER WATERSHED FLOOD RISK REPORT iii 2.5.16 Town Of Grafton Summary (CID 250306) ............................................................ 69 2.5.17 Town Of Harvard Summary (CID 250308) ............................................................ 72 2.5.18 Town Of Holliston Summary (CID 250195) .......................................................... 75 2.5.19 Town Of Hopkinton Summary (CID 250196) ........................................................ 78 2.5.20 Town Of Hudson Summary (CID 250197) ............................................................ 81 2.5.21 Town Of Lincoln Summary (CID 250199) ............................................................ 84 2.5.22 Town Of Littleton Summary (CID 250200) ........................................................... 87 2.5.23 Town Of Maynard Summary (CID 250204) .......................................................... 90 2.5.24 Town Of Natick Summary (CID 250207) .............................................................. 93 2.5.25 Town Of Northborough Summary (CID 250321) .................................................. 96 2.5.26 Town Of Sherborn Summary (CID 250212) .......................................................... 99 2.5.27 Town Of Shrewsbury Summary (CID 250332) .................................................... 102 2.5.28 Town Of Southborough Summary (CID 250333) ................................................ 105 2.5.29 Town Of Stow Summary (CID 250216) ............................................................... 108 2.5.30 Town Of Sudbury Summary (CID 250217) ......................................................... 111 2.5.31 Town Of Tewksbury Summary (CID 250218) ..................................................... 114 2.5.32 Town Of Upton Summary (CID 250340) ............................................................. 117 2.5.33 Town Of Wayland Summary (CID 250224) ........................................................ 120 2.5.34 Town Of Westborough Summary (CID 250344) ................................................. 123 2.5.35 Town Of Westford Summary (CID 250225) ........................................................ 126 2.5.36 Town Of Weston Summary (CID 250226) ........................................................... 129 4 Actions to Reduce Flood Risk ............................................................................................ 132 4.1 Types of Mitigation Actions ........................................................................................ 132 4.1.1 Preventative Measures .......................................................................................... 132 4.1.2 Property Protection Measures ............................................................................... 132 4.1.3 Natural Resource Protection Activities ................................................................. 133 4.1.4 Structural Mitigation Projects ............................................................................... 133 4.1.5 Public Education and Awareness