2018 Flood Mitigation Plan Update Howard County, Maryland October 1st, 2018 Howard County Flood Mitigation Plan October 1, 2018 (This page is intentionally blank) Page | 2 Howard County Flood Mitigation Plan October 1, 2018 Flood Mitigation Plan Howard County, Maryland October 1, 2018 Acknowledgements This Flood Mitigation Plan was prepared under the guidance of the County’s Department of Public Works–Storm Water Management Division, the Howard County Office of Emergency Management, and the Joint Steering Committee. The members of the Steering Committee are listed in Chapter 1. Prepared For: Howard County Department of Public Works Stormwater Management Division 6751 Gateway Drive, Suite 514 Columbia, Maryland 21046 Prepared By: Vision Planning and Consulting, LLC. 8171 Maple Lawn Blvd. Suite 245 Fulton, MD 20759 Phone: 240 893 8719 Fax: 888-872-9626 Email: [email protected] Page | 3 Howard County Flood Mitigation Plan October 1, 2018 (This page is intentionally blank) Page | 4 Howard County Flood Mitigation Plan October 1, 2018 TABLE OF CONTENTS CHAPTER 1: INTRODUCTION ................................................................................................................... 13 1.1 Background ..................................................................................................................................... 13 1.2 Study Area ...................................................................................................................................... 14 1.3 Plan Objectives .............................................................................................................................. 16 1.4 Planning Approach ........................................................................................................................ 16 1.5 Flood Mitigation Plan Participants ............................................................................................. 16 Flood/Hazard Mitigation Steering Committee ............................................................... 17 1.6 Planning Process ............................................................................................................................ 17 Step 1 – Organize work group and process .................................................................... 17 Step 2 – Assess hazards, risks, vulnerability, and mitigation capability ..................... 20 Step 3 – Develop a mitigation plan ................................................................................... 20 Step 4 – Implement the Plan .............................................................................................. 20 1.7 Organization of this Report ......................................................................................................... 21 CHAPTER 2: PROBLEM DESCRIPTION ................................................................................................... 23 2.1 Introduction .................................................................................................................................... 23 2.2 Sources of Flooding ...................................................................................................................... 24 Riverine Flooding .................................................................................................................. 24 Dam Failure ............................................................................................................................ 26 Stormwater Flooding ............................................................................................................ 27 2.3 Flood Measurement ...................................................................................................................... 27 Flood Levels ........................................................................................................................... 28 2.4 Hazards from Floods ..................................................................................................................... 28 During the Flood ................................................................................................................... 28 After the Flood ...................................................................................................................... 29 Impact to Buildings ............................................................................................................... 29 2.5 Vulnerability Assessment ............................................................................................................. 29 Methodology .......................................................................................................................... 29 Flood Loss and Vulnerability ............................................................................................... 30 Critical Facilities .................................................................................................................... 33 Spatial Distribution of Flooding ......................................................................................... 33 Potential and Average Losses ............................................................................................. 38 2.6 Repetitive Loss Properties ........................................................................................................... 40 Page | 5 Howard County Flood Mitigation Plan October 1, 2018 2.7 Economic Impact ........................................................................................................................... 40 Businesses .............................................................................................................................. 40 Impact on taxes ..................................................................................................................... 40 Transportation ....................................................................................................................... 41 Other impacts ........................................................................................................................ 41 2.8 Future Trends and Development ............................................................................................... 41 2.9 Conclusions..................................................................................................................................... 41 CHAPTER 3: PREVENTATIVE MEASURES .............................................................................................. 43 3.1 Introduction .................................................................................................................................... 43 3.2 Howard County Plan/Ordinance Review ................................................................................. 44 3.3 County Government, Departments, and Staffing Capabilities ............................................. 53 CHAPTER 4: PROPERTY PROTECTION ................................................................................................... 57 4.1 Introduction .................................................................................................................................... 57 4.2 Building Relocation ....................................................................................................................... 57 4.3 Acquisition ...................................................................................................................................... 58 4.4 Building Elevation .......................................................................................................................... 58 Advantages ............................................................................................................................. 58 Disadvantages ........................................................................................................................ 59 4.5 Barriers ............................................................................................................................................ 59 4.6 Dry and Wet Flood-proofing ...................................................................................................... 59 Advantages ............................................................................................................................. 60 Disadvantages ........................................................................................................................ 60 4.7 Sewer Backup Protection ............................................................................................................ 61 4.8 Flood Insurance ............................................................................................................................. 61 National Flood Insurance Program .................................................................................... 62 4.9 Mandates ........................................................................................................................................ 63 CHAPTER 5: PUBLIC EDUCATION AND AWARENESS ....................................................................... 65 5.1 Introduction .................................................................................................................................... 65 5.2 Map Information ............................................................................................................................ 65 5.3 Library and Web Sites .................................................................................................................