Subdivision Design and Flood Hazard Areas

The subdivision of land in or near floodplains involves the potential creation of tomorrow's flood risks. In an era of increasing attention to climate change, those risks may be greater than they have been in the past.

APA has a long history of addressing these issues, dating back at least to its 1997 publication of Subdivision Design in Flood Hazard Areas (PAS Report No. 473, 1997).

In partnership with the Association of State Floodplain Managers, and with funding from the Federal Emergency Management Agency, the new Subdivision Design and Flood Hazard Areas PAS Report provides updated guidance on the subject for local planners, consultants, and others involved in the subdivision design and site plan review process. The need is clear for much more technical guidance related to all aspects of subdivisions, from planning to design, to standards, to infrastructure maintenance, and this report provides that.

This new PAS Report benefits from a strong partnership between APA and ASFPM on a number of fronts. Both organizations have been leaders in the NOAA Digital Coast Partnership and are also partners on the Planning Information Exchange webinar series, which provides education on hazard mitigation planning. And we are exploring other areas as well that we consider grounds for potential fruitful collaboration. Planners and floodplain managers have many common goals, and our two organizations even have some overlapping membership. Both bring valuable expertise to this report.

The updated PAS Report focuses on the strict subdivision approach used in PAS Report No. 473 to include other land-use regulatory considerations affecting design in flood hazard areas, specifically including PUD regulations and design review, but also innovations in coastal and floodplain zoning and regulation, and the role of property owner associations. The report also includes a glossary and an appendix providing sample language from some of the best ordinances around the country.

Subdivision Design and Flood Hazard Areas (PAS 584)

This report provides updated guidance for local planners, consultants, and others involved in the subdivision design and site plan review process.

Why This Report?

Obviously, much has changed since APA's PAS Report 473, Subdivision Design in Flood Hazard Areas, was published in 1997. The Community Rating System was then still in its infancy, having only been developed in 1990. Sustainability and resiliency were just words found in the dictionary and not necessarily a focus of land development. No one had given much thought to adapting to our ever-changing climate. Project Impact was launched the same year, and the National Flood Insurance Program was approaching its 30th birthday in 1998.

Almost 20 years later, sustainability, resilience, climate change, and related topics are at the forefront of attention for planners, floodplain managers, and related professionals. However, subdivision practices have seen relatively little change, especially where they concern comprehensive floodplain management. The benefit provided by this report relates to this basic need.

APA, the nation's lead organization in the planning profession, and ASFPM, the nation's premier floodplain management organization, partnered to address the needs of the urban planning and floodplain management professions by providing modern-day assistance on "sound" subdivision guidelines and related regulatory practices such as planned unit development (PUD) design, emerging tools such as the coastal resilience zone, and issue areas such as climate adaptation and No Adverse Impact to name a few of the areas of emphasis.

The idea behind this update, in part, is to focus on breaking the build-damage-rebuild cycle our nation now finds itself in, to reduce risk from flood damages, and to incorporate best planning practice guidance, as well as other aspects of floodplain management. It is quite obvious that a community cannot be sustainable or resilient without safe places to live, work, and play.

One need merely look at the damage to the housing stock and the loss of life from Hurricanes Sandy and Katrina or events such as the Colorado flood of 2013 or the Atlanta flood of 2009, to see the need for and the practical utility of the update to PAS 473. It is about saving lives and protecting property at its foundation and about building a future for our residential communities that are free from, or at least have a reduced risk to, flooding.

Historic Report

The 1997 version of Subdivision Design in Flood Hazard Areas (PAS Report 473) is also available for download.

Symposium on Subdivision Design in Flood Hazard Areas

On February 19-20, 2015, APA convened a symposium focused on Subdivision Design in Flood Hazard Areas at its Chicago office.

The symposium focused on issues pertaining to the importance of planning subdivisions in flood hazard areas.

Invited participants were invited to discuss the overarching framework of the "five strategic points of intervention" in the plan-making process, defining issues of subdivision design in relation to flood hazard areas, defining the audience for the report, defining guiding principles for addressing subdivision design in flood hazard areas, and identifying best practice examples.

Symposium Summary

Over the course of the symposium, participants highlighted the importance of reducing risks on our nation's floodplains and defining guiding principles for subdivision design in flood hazard areas.

Hosted in partnership with the Association of State Floodplain Managers (ASFPM), the symposium convened subject matter experts in the fields of planning, hazard mitigation, and floodplain management to bring knowledge and perspectives into the discussion of subdivision design and flood hazard areas as APA works to update the 1997 PAS Report Subdivision Design in Flood Hazard Areas.

Attendees included subject matter experts along with Federal Emergency Management Agency (FEMA) representatives and APA and ASFPM staff.

This symposium marks the fifth venture into Planning Advisory Service (PAS) research between APA and FEMA. This project is funded through the National Flood Insurance Program, which helps carry out the mission of reducing risk in our nation's floodplains.

On February 19, the conversation kicked off with a discussion of why it is important to address this issue. It continued with a detailed discussion of the overarching framework of the "five strategic points of intervention" in the plan-making process, defining issues of subdivision design in relation to flood hazard areas, and defining the audience for the report.

On February 20, attendees focused in on defining guiding principles for addressing subdivision design and flood hazard areas and identifying best practice examples.

Strategic Points of Intervention

Many opportunities exist for planners and floodplain managers to make a difference throughout the strategic points of intervention in the planning process — and these provided the framework for the discussion. The five strategic points of intervention are defined as:

  • Long-range community visioning and goal-setting
  • Plan making (including comprehensive plans, subarea plans, and functional plans such as hazard mitigation or stormwater management plans)
  • Standards, policies, and incentives (subdivision regulations, design guidelines)
  • Development work (site plan review)
  • Public investments (capital improvements)

A comprehensive and integrated approach across these points of intervention is important to protecting natural features and areas such as floodplains; and aligning development with community goals, which can increase community sustainability and resiliency.

Defining the Issues

Attendees then discussed challenges to addressing the issues of subdivision design in flood hazard areas. These included:

  • The need for enforcement of existing regulations;
  • Improving capital improvements programs to better address stormwater needs;
  • Educating stakeholders on the issues and opportunities that exist when addressing good subdivision design practice and resiliency;
  • The need for coordination between organizations and agencies;
  • Ensuring that zoning regulations address the floodplain; and
  • Encouraging communities to look beyond the minimum requirements of FEMA's NFIP standards and regulations.

Workshop participants also discussed tools that communities are using, such as FEMA's Community Rating System (CRS), and the need to ensure that communities are aware of existing resources, such as the American Society of Civil Engineers (ASCE) Public Safety Guidance for Urban Stormwater Facilities.

Finally, workshop participants turned to the challenges posed by the increasing frequency of major flood events.

Guiding Principles

As attendees noted, the frequency of flood events is increasing. With this increased frequency, the importance of flood risk management also increases. While avoiding building in the floodplain altogether is the ideal, many communities already have structures located within a floodplain, face geographical or topographical constraints, or are approaching build-out, with few other options for development, requiring other actions to be taken.

On the second day of the symposium, workshop participants turned from the broader scope of the report to defining guiding principles for subdivision design related to flood hazard areas.

Participants identified a number of guiding principles and then prioritized them, with consensus around:

  1. The need for an integrated approach
  2. Maintaining the natural and beneficial functions (NBF) of the floodplain
  3. The need for resilient infrastructure, such as stormwater facilities and transportation networks.

Attendees also noted their second priority, with:

  1. Data-driven design and decision making
  2. The thoughtful use of protected open space emerging as the top two

Other guiding principles that emerged from this discussion included no adverse impact; the balance of tools and techniques comprising avoidance (moving out of the way) and resistance (taking actions to resist inundation); ordinances that enable compliance; and a watershed or ecosystems approach.

Based on the prioritization, attendees thought that the need for an integrated approach a part of a broad-based program that maintain NBF through a no adverse impact approach should serve as an overarching vision for the guiding principles of the report.

Summary and Next Steps

The discussion that took place during the symposium provided an in-depth analysis of the current state of subdivision design in flood hazard areas and the problems that need to be addressed. In addition to defining the major issues and guiding principles, attendees also discussed the primary audiences for this report, identified best practice examples, and helped APA and ASFPM draft a detailed outline of the PAS report.

Since the 1997 publication of the original PAS report, Subdivision Design in Flood Hazard Areas, flood damage in the United States has sprung from under $6 billion in the 1990's to $10 billion dollars in the 2000's with continued annual growth (ASFPM, 2013). The need is clear for more and current technical guidance related to all aspects of subdivisions, from planning to design, to standards, to infrastructure maintenance.

Symposium Participants

On February 19-20, 2015, the American Planning Association (APA) convened a symposium at its Chicago office that focused on Subdivision Design in Flood Hazard Areas.

Symposium Experts

Jerry BremsJerry Brems retired from the Licking County Planning commission after serving as its director for more than 19 years. During his tenure, Licking County became the first Ohio County to participate in the National Flood Insurance Program's Community Rating System. Licking County became the first "Project Impact" community in Ohio in 1998. Prior to working for Licking County, Brems worked for the Ohio Department of Natural resources in the Floodplain Planning Unit assisting communities participate in the National Flood Insurance Program and was responsible for drafting State of Ohio Floodplain Management Regulations. The regulations were ultimately adopted by the Ohio Department of Administrative Services for managing state activities in flood hazard areas.

Samuel D. BrodySamuel D. Brody is a professor and holder of the George P. Mitchell '40 Chair in Sustainable Coasts in the Departments of Marine Sciences and Landscape Architecture and Urban Planning at Texas A&M University. He is the director of the Center for Texas Beaches and Shores and co-director of the Institute for Sustainable Coastal Communities. Brody's research focuses on coastal environmental planning, spatial analysis, flood mitigation, climate change policy, and natural hazards mitigation. He has published numerous scientific articles and recently authored the book Rising Waters: The causes and consequences of flooding in the United States, published by Cambridge University Press. Brody teaches graduate courses in environmental planning and sustainable/resilient coastal development. He has also worked in both the public and private sectors to help coastal communities with environmental and flood mitigation plans.

J. William BrownJ. William Brown is the stormwater executive manager for the City of Arlington Texas. He is responsible for all stormwater and floodplain management related activities. Previously, he was an assistant city engineer for Greenville, South Carolina; senior project engineer in DuPage County, Illinois; and a hydrologic and hydraulic Engineer for Hey & Associates in Chicago. Brown holds an M.S. from Oklahoma State University in agricultural engineering and pursued graduate work at the University of Minnesota. He is past chair of the Illinois Association for Floodplain and Stormwater Management. From 2004-2008 he co-chaired the Mapping and Engineering Standards Committee for the Association of State Floodplain Managers and since 2008 he has co-chaired the Stormwater Committee. He is currently serving a four-year appointment on the federal Advisory Committee on Water Information.

Tiffany LydenTiffany Lyden is floodplain outreach specialist at the Montana Department of Natural Resources and Conservation. As part of the state's Floodplain Management program, she works cooperatively with FEMA and local communities to assistance communities with regulation updates and administration, new floodplain mapping projects, and other floodplain-related matters. Previously, she was a statewide lake specialist for the University of Wisconsin-Extension, a county planner with Lake County (Montana), and director of the Vilas County Land and Water Conservation Department in Wisconsin. In both Montana and Wisconsin, she has served on several state and regional committees on water policy and other resource-related matters. Lyden received a bachelor's degree in biology from Augustana College in Illinois in 1992 and a Master of Science degree in water resources from the University of Wisconsin in 2000.

Deborah MillsDeborah Mills is Dewberry, Virginia's hazard mitigation client manager, focusing on Dewberry's national Hazard Mitigation Practice and specializing in mitigation and resilience for critical infrastructure, neighborhoods, residences, and small businesses. Following 31 years of service to Virginia in forestry, water quality, and emergency management, she joined Dewberry where she has managed numerous mitigation projects. She represents ASFPM and the NEMA Mitigation Alliance on a variety of efforts, including co-chairing the ASFPM Mitigation Committee. She served on 16 federal disaster operations, including Hurricane Katrina. Mills is active in her downtown Richmond, Virginia, neighborhood, gardening, spoiling her rescue English Cocker Spaniel, and building disaster resistant Lego models with her godsons.

APA Team

Nick Ammerman, Library and Taxonomy Manager
Camille Fink, Senior Editor
Anna Read, Senior Program Development and Research Associate
David Rouse, AICP, Research Director
James C. Schwab, AICP, Manager of the Hazard Planning Center
Nicholas A. Walny, Hazard Planning Center Intern

ASFPM Team

Chad Berginnis, Executive Director
Bridget Faust, Project Research Specialist
Jeff Stone, Project Manager and Geographic Information System (GIS) Coordinator
Terri Turner, Development Administrator / Floodplain Manager / Hazard Mitigation Specialist for the Planning and Development Department in Augusta, Georgia

FEMA Team

Fred Kaehler, Floodplain Management and Insurance Branch Chief for FEMA Region 5
Eric Kuklewski, Risk Analysis Branch Chief for FEMA Region 5
Julia McCarthy, ‎Senior National Flood Insurance Program Specialist for FEMA Region 5
Kathleen Smith, Branch Chief for FEMA's Assessment & Planning Branch

Literature Review

American Society of Civil Engineers. Flood Resistant Design and Construction. 2006.

  • Updates standards for flood-resistant design and construction of structures in flood hazard areas. Does not specifically address subdivisions but is easily applicable to any type of structure.

Arendt, Randall G. 1996. Conservation Design for Subdivisions: A Practical Guide to Creating Open Space Networks. Washington, D.C.: Island Press.

  • Includes a four-step subdivision design process that incorporates identifying environmental factors like floodplains and advocates for keeping at least half of sites undeveloped.

Association of State Floodplain Managers. "A Guide for Higher Standards in Floodplain Management." 2010. Floodplain Regulations Committee. Available at http://www.floods.org/ace-files/documentlibrary/ committees/Insurance/ASFPM_Higher_Standards_Reference_Guide_1010.pdf.

  • Provides recommended language for floodplain management standards, including for subdivision development.

Atlanta Regional Commission. "Georgia Stormwater Management Manual (Volume 2)." 2001. Available at http://documents.atlantaregional.com/gastormwater/GSMMVol2.pdf.

  • Includes several examples and diagrams of subdivision design for stormwater management.

Barbedo, José, Marcelo Miguez, Dan van der Horst, and Monique Marins. 2014. "Enhancing ecosystem services for flood mitigation: a conservation strategy for periurban landscapes." Ecology & Society, 19 (2): 665-675.

  • Examines the impact of water-flow regulation services for flooding in areas immediately outside of cities.

Bozeman (Montana), City of. Subdivision Regulations. Available at www.municode.com/library/mt/bozeman/codes/code_of_ordinances?nodeId=PTIICOOR_CH38UNDECO (search by code #s: 38.41.060 and 38.31.090)

  • Subdivision regulations that specifically consider the impacts of flooding at a higher level of detail than most regulations.

Federal Emergency Management Agency. "Variances and the National Flood Insurance Program." 2014. Washington, D.C.: Federal Emergency Management Agency. Available at www.fema.gov/media-library-data/1415994328968-8a331cb33b4b5aeb3ab26f9d382a7f68/FEMA_P_993_FPM_Bulletin_Variance.pdf.

  • Federal guidance intended to help local government officials consider requests for variances and determining if a request meets the minimum requirements of the NFIP. Includes a short segment on subdivisions.

________. "Floodplain Management Requirements." Available at www.fema.gov/floodplain-management/floodplain-management-requirements.

  • A detailed study guide and desk reference written for local officials who manage their communities' floodplain management regulations. Includes some information specifically on subdivisions in Unit 5.

Foss, Asa. 2005. "Low Impact Development: An Alternative Approach to Site Design." PAS Memo, May/June. Available at www.planning.org/pas/memo/2005/may/

  • Considers the benefits of low-impact development for managing stormwater and wastewater. Notes one subdivision that has used this method.

Gallatin County (Montana) Subdivision Regulations. Available at www.gallatin.mt.gov/public_documents/fov1-0000f32f/1SUBDIVISION/REGS/SEC-10-JANUARY-2012.pdf.

Hostetler, Mark E. 2012. The Green Leap: A Primer for Conserving Biodiversity in Subdivision Development. Berkeley, Calif.: University of California Press.

  • Takes an environmentally conscious approach to irrigation, stormwater management, and other flood mitigation techniques in subdivisions.

Illinois Flood Plain Management Desk Reference. Illinois Association for Floodplain and Stormwater Management. Available at www.illinoisfloods.org/desk_reference.html.

  • Exhaustive collection of information for the floodplain manager, including subdivision regulations.

Jordan, Karen J. "The Use of Retention Ponds in Residential Settings." University of South Alabama. Available at www.usouthal.edu/geography/fearn/480page/02Jordan/Jordan.htm.

  • Describes the importance of retention ponds in subdivisions to prevent flooding.

Licking County Planning Commission. 2013. "Subdivision, Land Division, Development and Congestion Prevention Regulations for Licking County, Ohio."

  • Includes extensive guidelines for floodplain consideration in building subdivisions.

Listokin, David, and Carole Walker. 1989. The Subdivision and Site Plan Handbook. New Brunswick, N.J.: Center for Urban Policy Research.

  • A broad reference on creating subdivision and site plans. Includes discussion of flood hazards and building in floodplains.

McLean County, Illinois. "Storm Water Requirements of the McLean County Subdivision Ordinance." Available at www.mcleancountyil.gov/documentcenter/view/377.

  • A detailed ordinance requiring subdivision plans to include storm or flood water runoff channels or basins, including design standards.

Morris, Marya. 1997. Subdivision Design in Flood Hazard Areas. Planning Advisory Service Report no. 473. Chicago: American Planning Association.

Richards, Lynn. 2006. Protecting Water Resources with Higher-Density Development. Washington, D.C.: U.S. Environmental Protection Agency. Available at www.epa.gov/smartgrowth/pdf/protect_water_higher_density.pdf.

  • Summarizes the explanation for why higher-density development may be better for stormwater management at the watershed scale.

Stevens, Mark R., Philip R. Berke, and Yan Song. "Disaster-Resilient Subdivision Design: Evaluating the Potential and Performance of New Urbanism for Evaluating Flood Risks." 2011. Floodplains: Physical Geography, Ecology and Societal Interaction. Nova Science.

  • Discusses the results of a study into U.S. subdivisions that are within floodplain areas. The authors found no difference between conventional and New Urbanist subdivisions in terms of how they incorporate flood hazard mitigation techniques.

Supplementary Materials

Aerts, Jeroen C.J.H., and W.J Wouter Botzen. 2011. "Flood-resilient waterfront development in New York City: Bridging flood insurance, building codes, and flood zoning." Annals of the New York Academy of Sciences, 1227 (1): 1-82.

Allen, Stephen C., Christopher E. Moorman, M. Nils Peterson, George R. Hess, and Susan E. Moore. 2012. "Overcoming socio-economic barriers to conservation subdivisions: A case-study of four successful communities." Landscape & Urban Planning, 106 (3), 244-252.

________. 2013. "Predicting success incorporating conservation subdivisions into land use planning." Land Use Policy, 33: 31-35.

Arendt, Randall. 2004. "Linked landscapes. Creating greenway corridors through conservation subdivision design strategies in the northeastern and central United States." Landscape and Urban Planning, 68 (2): 241-269.

Association of State Floodplain Managers.

Berke, P.R., D.J. Roenigk, E.J. Kaiser, and R. Burby. 1996. "Enhancing plan quality: Evaluating the role of state planning mandates for natural hazard mitigation." Journal of Environmental Planning & Management, 39 (1): 79-96.

Brandes, Donald H., and J. Michael Luzier. 1991. Developing Difficult Sites: Solutions for Developers and Builders. Washington, D.C.: Home Builder Press.

Burby, R.J. 1998. "Natural hazards and land use: An introduction" in Cooperating with nature: Confronting natural hazards with land-use planning for sustainable communities. R.J. Burby (ed). Washington, D.C.: Joseph Henry Press.

Burby, Raymond J., Robert E. Doyle, David R. Godschalk, and Robert B. Olshansky. 2000. "Creating Hazard Resilient Communities through Land-Use Planning." Natural Hazards Review, 1 (2): 99-106.

Design Manual for Retrofitting Floodprone Residential Structures. 1986. Washington, D.C.: Federal Emergency Management Agency.

Environmental Law Institute. "Protecting Wetlands and Wildlife Habitat While Reducing Flood Losses: A Guidebook on Interagency Collaboration in the Mississippi River Basin." 2012. Available at: www.eli.org/research-report/protecting-wetlands-and-wildlife-habitat-while-reducing-flood-losses-guidebook.

Fairfax County Department of Public Works and Environmental Services. 2014. "Floodplan Management Plan: Part of the Northern Virginia Regional Hazard Mitigation Plan." Available at www.fairfaxcounty.gov/dpwes/publications/stormwater/floodplain_progress_report.pdf

Godschalk, D.R., E.J. Kaiser, and P.R. Berke. 1998. "Integrating hazard mitigation and local land use planning." In Modernizing State Planning Statutes: The Growing Smart Working Papers, Vol. 2. Planning Advisory Service Report no. 480-481. Chicago: American Planning Association. 57-81.

Göçmen, Z. Aslıgül. 2013. "Research paper: Barriers to successful implementation of conservation subdivision design: A closer look at land use regulations and subdivision permitting process." Landscape and Urban Planning, 110: 123-133.

________. 2014. "Assessing the Environmental Merits of Conservation Subdivision Design." Journal of Planning Education and Research, 34 (2): 203-220.

Highfield, Wesley E., and Samuel D. Brody. 2013. "Evaluating the Effectiveness of Local Mitigation Activities in Reducing Flood Losses." Natural Hazards Review, 14 (4): 229-236.

Holway, Jim, Don Elliott, and Anna Trentadue. 2014. "Arrested Developments: Combating Zombie Subdivisions and Other Excess Entitlements." Lincoln Institute of Land Policy. Available at www.lincolninst.edu/pubs/dl/2339_1679_Arrested_Developments.pdf.

Hong-wei Lu, He Li, Du Peng, and Zhang Yi-mei. 2014. "An Inexact Sequential Response Planning Approach for Optimizing Combinations of Multiple Floodplain Management Policies." Polish Journal of Environmental Studies, 23 (4): 1245-1253.

Kousky, Carolyn, and Margaret Walls. 2014. "Floodplain conservation as a flood mitigation strategy: Examining costs and benefits." Ecological Economics, 104: 119-128.

Lichtenberg, Erik, and Ian Hardie. 2007. "Open Space, Forest Conservation, and Urban Sprawl in Maryland Suburban Subdivisions." American Journal of Agricultural Economics, 89 (5), 1198-1204

Mandarano, Lynn. 2010. "Sustainable land-use planning: revitalising a flood prone office park." Journal of Environmental Planning & Management, 53 (2): 183-196.

Mazzei, Vincent J. 2008. The new flood hazard area control act rules. Available at www.nj.gov/dep/landuse/lawsrules/fhacar_index.html.

Olshansky, R.B., and J.D. Kartez. 1998. "Managing land use to build resilience." In Cooperating with Nature: Confronting Natural Hazards with Land-use Planning for Sustainable Communities. R. Burby, Ed. Washington, D.C.: Joseph Henry Press/National Academy Press.

Porse, Erik 2014. "Risk-based zoning for urbanizing floodplains." Water Science & Technology, 70 (11): 1755-1763.

Tetra Tech. 2010. King County Flood Control District, Hazard Mitigation Plan. Available at http://your.kingcounty.gov/dnrp/library/water-and-land/flooding/local-hazard-mitigation-plan-update/KCFCD_HazardPlan_Mar2010.pdf.

Watson, Donald, and Adams, Michele. 2010. Flooding, in Design for Flooding: Architecture, Landscape, and Urban Design for Resilience to Flooding and Climate Change. Hoboken, N.J.: John Wiley & Sons, Inc.

Weisz, Reuben N., and John C. Day. 1975. "A Regional Planning Approach to the Floodplain Management Problem." Annals of Regional Science, 9 (3): 80-92.

Wetmore, F., and Jamieson, G. 1999. "Flood mitigation planning: The CRS approach." Natural Hazards Informer, 1 (July): 1–15.

Prepared by Nick Ammerman, Library and Taxonomy Manager, American Planning Association