What is a floodplain and why does it matter? A floodplain is the area of land adjacent to a stream or river which stretches from the banks of its channel to the base of the enclosing valley walls and which experiences flooding during periods of high discharge. A floodplain serves a very important purpose. It provides additional area for the movement of water from a storm when its runoff exceeds the channel capacity of a stream or river. Fortunately, the inundation is temporary and the water does return to the channel. The problems occur when we start to make changes to these areas for other purposes without addressing the impacts of those changes.
Due to the magnitude of losses incurred from historic flood events, the federal government initiated a program to limit development within the floodplains. The Federal Emergency Management Agency (FEMA) is the organization in charge of that program. The National Flood Insurance Program (NFIP) was established to reduce the losses typically associated with structures built within the floodplain. FEMA regulates the guidelines which participating communities agree to follow within their local jurisdictions. The communities and their residents benefit from the arrangement by having access to flood insurance, federally funded loans and access to grants to address areas prone to flooding.
Just because your property is in a floodplain does not necessarily eliminate the development potential in the consideration of a project. Each floodplain has defining characteristics that will dictate what can and cannot be constructed within its boundaries. Local floodplain ordinances, depths of flooding, water velocities, and existing development both upstream and downstream, to name a few, are factors to be considered in the evaluation of a property.
For anyone seriously considering a construction project within a floodplain, the first course of action should be to engage a floodplain expert. A floodplain expert will have experience in developing floodplain boundaries in accordance with the techniques prescribed by FEMA. They will have experience working with natural stream channels, understanding the issues and impacts of channel modification in cooperation with Floodplain Administrators (FPA) to address site specific requirements in obtaining project approval.
Richard Frithiof, PE, CFM specializes in floodplain management whose wide-ranging knowledge complements the hydraulic and hydrologic services Dunaway offers our clients. Richard offers design solutions that maximize dollars and minimize ongoing maintenance costs for floodplain mapping, dam design, stream restoration, erosion repair, flood analyses, and channel design projects. Richard’s expertise in the project review and permitting process of Federal Emergency Management Agency and the Texas Commission on Environmental Quality ensures clients an efficient process. His day-to-day involvement in all project phases, from initial property evaluation through post construction floodplain mapping, provides a continuously evolving body of relevant and practical knowledge.
 Goudie, A. S., 2004, Encyclopedia of Geomorphology, vol. 1. Routledge, New York. ISBN 0-415-32737-7