Possible Points: 100 points for the element.

Purpose of Element: For many communities in the U.S., flooding is not the only hazard that individuals and businesses that develop on the banks of rivers or along the coast are vulnerable to. For example, riverine floodplains can also be areas threatened by mudflows, ice jams and channel migration. The purpose of this element is to reward communities for implementing regulations that seek to manage development in areas that are subject to special flood-related hazards such that their impacts are minimized. This element has six sub-elements that are credited under the CRS program.

These sub-elements are:

  1. Prohibition of buildings,
  2. Ice jam regulations,
  3. Closed basin lake hazard regulations,
  4. Mudflow hazard regulations,
  5. Land subsidence regulations, and
  6. Uncertain flow path regulations, which includes channel migration.

Each sub-element has separate requirements and credit criteria. For more information on the special flood related hazards that are eligible for credit under this element and how they are scored, see pages 430-38 - 430-46 of the CRS Coordinator’s Manual.

For this element, credit is rarely requested for hazard regulations other than those that apply to channel migration. As a result, this element profile will limit its discussion to the requirements of this element as they pertain to channel migration regulations. A maximum of 80 points can be granted for managing development in channel migration hazard zones. Credit is granted for implementing one of the three following regulatory standards:

  1. 80 points are awarded if a community completes and maps a detailed study of migration potential, and prohibits development within this mapped area;
  2. 65 points are awarded if all developments are required to be located a safe distance away from a channel that could potentially migrate and are designed to be safe from channel migration; or
  3. 40 points are awarded if a channel setback is mapped and development within that area is prohibited until a detailed channel migration study has been completed.

Impact Adjustment: Yes. The impact adjustment for this element is calculated by taking the ratio of the area that qualifies for Special Flood-Related Hazard Regulations credit to the area of the regulatory floodplain.

Potential to Double Count Credit: Yes. If creditable areas are also protected through development limitations additional credit can be claimed for element 432.a. Development Limitations. In addition, if these areas are zoned at a low density or if conservation development techniques like cluster development are incentivized additional credit can be claimed for elements 422.f. Open Space Incentives and 422.g. Low Density Zoning.

Degree of Difficulty - Documentation: Low. Communities must assemble minimal amounts of documentation for this element. The required documentation includes a copy of relevant ordinances, proof that the community has fulfilled the prerequisites for this element, and an impact adjustment map.

Degree of Difficulty - Implementation: High. A prerequisite for this element is earning credit for mapping areas subject to channel migration. Oftentimes a licensed geologist, surveyor or engineer is needed in order to create these maps. Many communities will not have staff capable of creating these maps alone and will need to hire a contractor to assist with this task. This element also requires communities to pass more stringent development regulations in areas that are subject to channel migration. This could be met with resistance from the community, and the amount of effort associated with earning credit for this element is high.

Tip for Success:

  1. Contact your state’s NFIP coordinator or floodplain manager to determine if your state maps channel migration zones and/or other flood hazard areas. For example, Montana has mapped several major channel migration zones (“Channel Migration Zones,” n.d.). While other states, like Washington, have laws in place that require communities to study channel migration zones (Legg and Olson, 2014). Because mapping channel migration zones and other flood hazard areas is a prerequisite for earning CRS credit under this element, communities in which these maps have already been created are at a significant advantage.

Co-benefits Associated with this Element: Managing development in channel migration zones has several obvious benefits including reducing loss of life and property when flooding occurs. In addition, protecting homes, business and critical facilities through more stringent development regulations is essential to enhancing community resilience. Implementation of more stringent development regulations in channel migrations zones can also help to protect the integrity of the physical processes and defining characteristics of inland waterways and water bodies. For example, developing an appropriate distance away from channels that are known to migrate allows rivers to function as they would have prior to development, creates diverse habitats for fish and wildlife, and protects the historic floodplain of the river ("Channel Migration Easement Program," n.d.; Legg and Olson, 2014).