Over the past decade, local government agencies and floodplain management professionals have taken a strong interest in identifying, mapping, managing, and mitigating urban flood hazards and, ultimately, reducing flood losses in unmapped areas. Where these flood-prone urban areas have been identified, strategies to address localized flooding typically come with very high capital improvement costs or feasibility challenges that are increasingly difficult to overcome.
Urban Flood Hazards: Challenges and Opportunities explores the challenges of urban flooding, outlines concepts related to planning and mitigation to reduce future flood losses, and provides recommendations at the local and national scale to address urban flooding in communities nationwide.
Developed by ASFPM’s Stormwater Management Committee, this discussion paper:
- Provides an overview of the challenges associated with urban flood hazards
- Offers a framework to assess, identify, plan, mitigate, and manage urban flood hazard areas to reduce future flood losses
- Suggests recommendations on the local and national scales to assist communities with identifying and mitigating urban flood hazards
Urban Flood Hazards: Challenges and Opportunities focuses on one specific area of urban flooding, mainly areas outside of riverine and coastal flooding zones that are inundated due to surface runoff, i.e. areas where excess stormwater runoff exceeds the conveyance capacity of pipe and roadway systems, resulting in flooding that inundates structures and prevents safe access for emergency vehicles and personnel. The paper is intended for local stormwater and floodplain managers, but also serves as a valuable reference for all engineering and planning professionals within the floodplain and stormwater community.
“Floodplain stewards and stormwater managers face significant challenges in communicating urban flood risk due to the technical challenges and high costs associated with mapping these complex hazard areas. Even when the hazard has been mapped, they may also face internal and external communication challenges in getting the public, senior government leadership, and politicians to acknowledge the associated risk. An additional communication challenge is overcoming a lack of willingness to make flood map information available to the public because of concerns regarding negative perceptions of flood insurance requirements, adverse impacts to property values, and public calls to fix the problem immediately in the absence of adequate government resources.”
The 34-page discussion paper is divided into five sections, with the majority of pages dedicated to options for addressing the issue. Here the authors offer a detailed framework for confronting the myriad of issues around urban flooding while explaining the specific challenges related to mapping urban flood hazards. The paper also offers detailed advice on how to develop a comprehensive risk communication, education, outreach plan.
Urban Flood Hazards: Challenges and Opportunities concludes with six recommendations, which are explored in greater detail in the paper.
- Identify and Map Urban Flood Hazard Areas
- Manage Urban Flood Hazard Areas at the Local Level
- Communicate Urban Flood Hazards and Risk
- Develop Local Building Construction Standards
- Employ Multi-Generational Approaches to Implementing Improvements
- Identify Flood Mitigation Funding for Urban Flood Inundation Areas
As the paper notes, Gilbert White’s maxim that “Floods are ‘acts of God,’ but flood losses are largely acts of man” is particularly instructive for planning. Water finds a way to flow (down the path of least resistance), regardless of whether that area is developed or in a natural state. Human-scale disasters most frequently occur in areas where land is developed.