The Federal Emergency Management Agency (FEMA) has established regulatory floodways, which are the channel or thalweg of a river or other watercourse including the channel’s adjacent banks and floodplain fringe areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height. Any projects within a regulatory floodway are limited to zero (0) feet of rise or impact to the 1% annual chance (100-year) base flood elevation and all activities within a regulatory floodplain must seek approval from the local floodplain manager before construction or improvements can begin. Regulatory floodways are designated to discourage development within them and to ensure property upstream of a proposed project isn't adversely affected by any downstream improvements.
All projects in the regulatory floodway must be reviewed to determine if the project will increase flood heights (this is called an ”encroachment review”). Before a building permit can be issued, an engineering analysis often called a no-rise analysis or no-impact analysis must be conducted to determine the effect on flood flows and to ensure the project does not cause any restrictions or encroachments into the floodplain or reduce the base flood discharge.
Flood and Coast Engineering has the necessary tools and expertise to conduct a no-rise analysis or no-impact analysis for your existing or proposed development. We have experience with conducting both simplistic (narrative based) and technical (hydrology and hydraulic numerical modeling) analysis that can determine whether or not your proposed project will meet local floodplain building requirements. We will be happy to discuss your project in detail, so feel free to reach out to see how the engineers at Flood and Coast Engineering can assist.