The Department of Water Resource (DWR) Floodplain Evaluation and Delineation Program supports the FloodSAFE California Initiative by reducing the consequences of flooding through flood risk identification, and includes work to estimate the frequency, depth, and limits of potential flooding throughout California. This technical information assists with the development of floodplain analyses and assessment tools that can be utilized to support FloodSAFE programs and projects. The Floodplain Evaluation and Delineation Program supports the following projects:
· Alluvial Fan Floodplain Evaluation and Delineation (AFFED)
Alluvial Fan Floodplain Evaluation and Delineation (AFFED)
The AFFED Project provides local agencies making land-use decisions with the necessary tools to understand the characteristics and potential hazards of alluvial fan floodplains. The Project focuses on providing alluvial fan floodplain delineations in 10 Southern California counties. The ten Southern California counties participated in the Alluvial Fan Task Force. The floodplain maps will be developed in partnership with the California Geological Survey (CGS) and local agencies such as the Ventura County Watershed Protection District and the Riverside County Flood Control and Water Conservation District.
The Project will focus on alluvial fan areas subject to future development within the next five years. The selected study areas do not have an existing Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map used by the National Flood Insurance Program. The Project’s objective is to reduce future flood losses in active alluvial fan areas through risk informed land use decision making. To accomplish this, floodplain maps will be developed to indicate areas of potential flooding and flood-flow sedimentation hazards. The maps developed from this process and the procedures described are advisory, but can be made regulatory if the community links the maps to their community floodplain management ordinance or requests that that FEMA incorporate the maps into the National Flood Insurance Program.
The Project will coordinate and collaborate with FEMA, the local communities, and the California Geologic Survey to identify high priority areas for mapping, define active and inactive areas of alluvial fans, identify alluvial floodplain hazards, and develop alluvial floodplain maps. Coordination meetings have taken place and will be scheduled throughout planning and implementation of the Project to ensure stakeholders’ input is incorporated into the study design.
Risk informed land use planning is one of the most effective ways to reduce the consequences of floods. In particular, Assembly Bill 162 (2007) which applies statewide and Senate Bill 5 (subsequently amended in 2012 by Senate Bill 1278 and Assembly Bill 1965) which applies to the Sacramento-San Joaquin Valley call for amendments to local city and county general plans and zoning ordinance and mandate findings be made in flood hazard zones (i.e., FEMA 100- and 500-year floodplains) before the approval of certain land use decisions. The Policy/Planning Project is designed to assist communities to comply with the local land use legislation by providing tools, data, and analyses to amend their general plans, associated plan elements, and local zoning ordinances. In 2010 DWR prepared a guidance document entitled “Implementing California Flood Legislation into Local Land Use Planning: A Handbook for Local Communities” (Handbook) that assists cities and counties comply with the new legislation by identifying and interpreting the provisions of the applicable code sections, and provides references for data and technical assistance for flood risk planning. This project includes updating of the Handbook as new information is developed such as the Central Valley Flood Protection Plan adoption in June 2012 and the recent flood legislation that affects land use planning requirements.
The Project will also assist local communities update their floodplain management ordinance to reflect the State’s adoption of the International Building Codes and related building code appendices. The project will also assist communities improve their level of participation in the National Flood Insurance Program Community Rating System. The Project will also assist communities develop effective hazard mitigation grant applications for submission to the California Emergency Management Agency and FEMA for funding consideration.
The Project is designed to assist local communities reduce the risk to life and property caused by floods. This is achieved by improving policies and land use planning decision making. This objective will be achieved by incorporating flood risk and mitigation of flood risk into the development of community General Plans, General Plan updates, improvement of the community floodplain management ordinance, improved level of participation in the NIP Community Rating System, development of effective multi-hazard plans, and applying for funding to implement cost-effective flood hazard mitigation projects.