In a floodway analysis, how much can the fringe be obstructed before the base flood level increases?

In a floodway analysis, it is essential to maintain the integrity of the floodplain to prevent an increase in base flood levels. The correct answer, indicating that the fringe can be obstructed by 1 foot before a base flood level increase occurs, is based on the regulatory stipulations set forth by FEMA.

This 1-foot criterion is a critical component in managing flood risks and ensuring that any modifications or developments within the floodway do not significantly impact the flow of water during a base flood event. It is designed to prevent increased flooding risks to neighboring properties and communities by ensuring that any obstruction is minimal and within acceptable limits. Beyond this threshold, even minor obstructions could result in a change to the floodplain's hydrology, which may lead to more significant adverse effects, like increased flood elevations.

Understanding this constraint is crucial for floodplain management practitioners as they assess development proposals and conduct floodplain analyses to ensure compliance with the National Flood Insurance Program (NFIP) requirements. It emphasizes the balance that must be maintained in floodplain management between development needs and the protection of life and property from flood hazards.