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3.2 Floodplain Management There are several unresolved floodplain management issues which were brought to the surface as a result of the recent flooding on Fall River. These issues include the lack of a for- mal insurance zone for dam failure floods, the very low number of insured properties in Estes Park and the state, the availability of floodplain mapping, and the adequacy and enforcement of local floodplain management regulations. Other floodplain management issues that have become apparent are the lack of a State program to acquire floodplain land for open space, management of State owned property in the floodplain, and the design of private bridges in the floodplain. 3,2.1 Dam Failure Flood Zone The flood on Fall River was, on the average, about 2 1/2 times as deep as the estimated 500-year flood stage, Flood waters greatly surpassed the 500-year flood boundaries indicated in the town's flood insurance study, since the regulation of floodplains in the united States is based on the 100-year flood, the extent of flooding which may be expected to occur below a reservoir as the result of a darn fail- ure has not, with few exceptions, been included in federal or State conducted floodplain studies. In response to specific local requests, the CWCB has pro- vided assistance to local communities by requesting the Soil Conservation Service to make a detailed study on the extent of flooding in the event of a dam failure, The SCS has conducted detailed dam flood studies and on Box Elder Creek in Weld County, Flood insurance rate maps, which are a product of the federally subsidized flood insurance program, take into account only flooding fram natural runoff and precipitation events, In fact, as a matter of common practice, most engineers will exclude from the calculation of peak discharge the drainage area above any dam built with and operated for flood control bene- fits. This will indicate lower peak discharges from rainfall due to a reduction in basin area. Otherwise the presence of a dam in flood hydrology studies is essentially ignored by assuming the reservoir at normal operating level and routing the flood through the emergency spillway. Evaluation of the flood hazards of existing or proposed dam should they break would assist planning for development in down- stream areas and help emergency preparedness and rescue agencies prepare for disasters, Due to lack of funding, however, the State has never been able to implement a program for methodically evaluating the flood hazards associated with the failure of dams in Colorado, 57