Approved by the Energy, Environment, and Water Policy Committee on February 24, 2021
Approved by the Public Policy and Practice Committee on May 4, 2021
Adopted by the Board of Direction on July 16, 2021


The American Society of Civil Engineers (ASCE) recommends governments at all levels to adopt proactive floodplain management policies that:

  • Hold paramount the public’s safety, health, and welfare. 
  • Protect and restore natural floodplains. 
  • Regulate land use and discourage development in floodplains.
  • Inform residents and community planners of the risk associated with development in both floodplains and develop flood disaster mitigation plans. 
  • Support creative partnering between all levels of government to adopt floodplain management policies.
  • Fund the design and implementation of floodplain management policies and flood mitigation projects, both structural and non-structural. 
  • Incorporate the concept of building disaster resistant communities consistent with sustainable development.
  • Encourage risk appropriate, multiple uses of flood prone areas.
  • Pursue nonstructural flood mitigation facilities, including river restoration, and wetland restoration that include improvements in habitat, ecosystems, recreation, and open space use.
  • Consider relocation as a strategy for communities that cannot be protected.
  • Encourage the use of social equity for disadvantaged communities and at-risk areas in floodplain management decisions.


Development and associated infrastructure in flood prone areas has increased rapidly as people are attracted to historically fertile floodplains and coastal areas, and lower land costs. Compounding the quantity of property at risk, there have also been increases in the magnitude and frequency of flooding as a result of changing precipitation patterns. Even though the benefits of preserving the natural floodplains as flood storage areas and wildlife habitat have been recognized, floodplains continue to be developed and new inhabitants are subjected to periodic flooding and related devastation. People living and working in flood prone areas often have developed a false sense of security. Once a flood occurs, residents and businesses often expect government to reduce or eliminate the risk of flooding through large capital projects. These populations need the protection of an efficient floodplain management program implemented before the flood occurs. By recognizing the likelihood of future flooding and the beneficial aspects of the natural floodplain, areas can be protected, and communities can become disaster resistant or can be relocated when protection cannot be assured. 

Floodplain management includes the operation of an overall program of corrective and preventive measures for reducing flood damage, including, but not limited to, emergency preparedness plans, land use policies, buy-out of flood prone structures, and flood risk reduction systems. Truly effective floodplain management is not limited to the traditional 100-year FEMA floodplain definition, but considers the whole range of possible flood scenarios, including more extreme events. Floodplain management should consider both monetary and social benefits.

It has been repeatedly demonstrated that the cost of well-planned mitigation efforts is far less than the expense of repair to damaged property. According to the National Institute of Building Sciences “Natural Hazard Mitigation Saves: 2019 Report” released in December 2019, every dollar spent on mitigation translates into an average savings of $6 for the American public.


Throughout the U.S., significant populations and property are currently at significant risk from flooding. Much of the development, and residents at risk, occurred prior to modern floodplain development approaches and regulations. Effective floodplain management works to both mitigate the existing risk and to prevent or minimize the creation of future risk.  This requires a balanced approach to:

  • AVOID future risk through land use controls that keep people out of and property from being built in harm’s way through prohibitions and required protection levels. 
  • REDUCE existing risk through structural projects such as channel improvements, levees, detention and other flood control structures or projects.
  • MITIGATE individual property risk through programs such as elevation of existing structures and demolition, and rebuilding of non-compliant structures.
  • RESTORE natural floodplains and riparian zones primarily through buyouts and restoration activities.

It is the responsibility of civil engineers to provide appropriate planning to reduce risk in order to save lives and property and to educate the public on existing risks.

ASCE Policy Statement 421
First Approved in 1994