Final answer:
A builder cannot legally allow for any increase in base flood elevation when constructing in a floodway. They must provide evidence that the proposed project will not increase flood levels, adhering strictly to floodplain management regulations.
Step-by-step explanation:
When considering the construction of a house within a floodway, it's essential to understand how much the project can increase the base flood elevation (BFE). According to regulations, typically, new constructions in floodways are not permitted unless it is demonstrated that it will not result in any increase in flood levels during the occurrence of the base flood discharge. Builders must conduct a detailed analysis to ensure their project complies with these regulations, and any deviation can lead to significant environmental and property insurance implications.
A flood event is often measured in terms of the cubic feet per second (cfs) of water flow, and this flow can be used to determine the recurrence interval of different-sized floods through a discharge-recurrence interval graph. A flood stage occurs when water levels exceed the capacity of the river bank, and adding structures like houses can influence the flow and elevation of a potential flood.
Considering the flooding risks and potential for damage to both property and local ecosystems, the build must be approached with thorough planning and adherence to floodplain management regulations. Local ordinances and federal guidelines, such as those from FEMA, specify constraints and requirements for construction in such areas.