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II I I I I I I I I I I I I I I I I I I The use of the one foot rise floodway arises from the fact that FEMA defines its floodway as such. FEMA's definition of the floodway, from 44 CFR Part 59 is: The channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the loo-year flood without cumulatively increasing the water swface elevation more than one foot at anyone point. The authors of the model ordinance (included in Appendix B) acquired funher clarification of the one foot rise floodway as follows: Consultations with the FIA and the Corps of Engineers confirmed that the one foot increase is used in the initial determination of the floodway itself and is not meant to allow a subsequent heightening of the loo-year flood elevation, once the limits of the flood way have been so set. That is, in order to detennine that portion of the floodplain which will be designated as the flood way, one begins at the outer limits of the floodplain and assumes full development inward, toward the river or stream channel, on both sides of the flood hazard area, until the point is reached where development will cause the loo-year flood elevation to rise by one foot. The area remaining between this boundary and the channel is the floodway, and because any further development here would necessarily increase the loo-year flood elevation by more than one foot, no such development can be countenanced. Boulder and the UD&FCD have designated a half foot rise floodway, and Boulder currently has further resnictions defined as a 2 foot deep or 2 feet per second flood way. An advantage to a more stringent flood way regulation is that it offers an additional level of protection to the public's health, safety and welfare. The City of Boulder is situated in a location that is subject to flash flooding, unlike other communities in the United States. There may be little time to evacuate residents in the floodplain during an extreme flood event, especially along the Boulder Creek nibutaries. There are high debris loads in flash flood waters. Sningent floodway regulations restrict development in high hazard areas where property could be destroyed or damaged and where the potential for loss of life is high. This type of regulation protects unwary buyers from victimization and protects properties upstream, downstream, and laterally from obstructions which would raise flood heights, divert waters to new areas, increase velocities, or hann areas that otherwise would not have been hanned. In addition, more stringent floodway regulations avoid the need for public expenditure for the construction of flood protection channelization projects; avoid the need for extra public expenditure for disaster relief after the flood; and minimize community disruption and economic losses after the flood. PRODUCT NUMBER ANALYSIS General Any flood hazard analysis based upon hazard to human life must make many assumptions. Considerations in this analysis include design body configuration, resultant hydraulic forces, and footing. Factors not considered in this analysis are variations in strength, agility, balance, center of gravity, destabilizing impacts from floating debris, variable body configuration, emotional reaction, and other human factors. These factors are difficult to quantify in the context of this analysis and therefore were omitted from consideration. Our research could nOllocate published technical data on this subject. Those factors we considered provide a means to quantify the hazard from flood waters to human life due to instability in the fonn of a "toppling moment", "slippage", and "buoyancy". -4-