How are Floodway limits defined.

[wds1]

The Floodway is the portion of the floodplain that is reserved for the passage of the 100 yr. storm without raising the flood elevation by more than 1.0 feet. You cannot fill in the floodway, but you may fill-in the remainder of the flood plain(flood fringe). It appears that the location is arbitary. In other words, as long as you reserve enough space for the 100 yr storm, you can locate it anywhere in the floodplain. Some Floodway maps show the floodway shift to all one side of the stream. In general the highier velocity areas are more efficient. My question is this. If we have a Floodway study performed and it interferes with our proposed building, can we shift the floodway to miss our building? Fema's definition of Floodway does Not define the Floodway location. It only defines the flow and peak elevation.

 

[cimmeron]

The floodway is determined as part of the HEC 2 calculations mostly by intelligent trial & error. The flood plain is restricted in the computer program by degrees until the flood level is no more than one foot higher. The engineer has some leeway in positioining the flood way, but it location is mostly deterined by the hydraulics of the channel since the flood level is determined by both the voume of flow and veloicty.