Converting a NEXRAD Rainfall Map into a Flood Inundation Map by ...

The aggregation of floodplain inventories into coarse land uses allows forthe use of case specific flood depth-damage curves obtained for each land usethrough field studies and floodplain inventories and representing one of the threebasic functions (as described in section 2.1) needed to perform the traditionaleconomic evaluation for flood damage assessments. These empirical depthdamagecurves are normally developed by a property survey of the floodplain andby individual or aggregated estimates of depth versus damage for each land usecategory in the floodplain.The HEC-FDA system provides for a somewhat less aggregated approachto evaluate the depth-damage relationship. In it, each structure is given aparticular depth-damage assessment based on a more detail definition of theproperties’ first floor and ground levels. Specification of first floor stages andbeginning damage depth stages for each property in the inventory allow for amore realistic approach. However, the depth-damage relationship is aggregated ateach damage index location station and the effect of a given depth at the indexlocation relies on very good quality field surveys and evaluations. This approacheven though more realistic relies on very hard to get depth-damage relationshipsthat can quickly become obsolete given the dynamic nature of floodplainsregularly affected by new regulations, alleviation plans, and changing land useconfigurations. So, even though the HEC-FDA provides a distributed approachfor definition of depth-damage curves (based on a distributed structure inventory)it aggregates the spatial inventory of the floodplain into reach index locationsconfiguring a lumped damage assessment methodology.18