Levee Length vs. FLO-2D Levee Length

A new feature of the GDS helps account for flow overtopping a levee. When the user assigns the levee by polygon over a long distance, then the actual portion of the levee in the grid element may be shorter than the Levee component. The levee component length is assigned using the GE Width * 0.41412 (this is the length of the octagon side). For example, if a grid element has a levee assigned to 3 directions, the levee crest length is 3 x 0.41412 x GE Width. If the physical levee is a straight line across the grid element the calculated discharge length could be too long.

The discharge computed over a broadcrested weir (Q = C*L*H^1.5 and L would be the levee crest length) This length might be too long using all three sides. This can be corrected by adding a WRF value to the side of the grid element. The GDS does this automatically for the "polylines" by computing the entire length of the levee and assigning the appropriate WRF value to the individual grid elements.