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X II-6 Non-Structural The non-structural approach to flood damage reduction consists of regula- tions, flood warnings, floodproofing, and public information. This approach requires an adjustment by floodplain occupants to the flood hazard rather than a reduction in the depth or extent of flooding itself. All of the local governments along the South Platte River are currently participating in the National Flood Insurance Program. A key condition to participating in this program is the adoption and enforcement of adequate floodplain regu- lations to insure that all future development will be located at or above the 100-year flood level. In return for floodplain regulation, floodplain occupants within the participating communities along the river are eligible to purchase flood insurance. Flood insurance can mitigate the financial hardships that result from flood damage. warnings by the National Weather Service may not provide adequate time for floodplain residents to take appropriate steps. Flood warnings must be specific as to time and peak elevations and must be accurate in order for floodplain occupants to react effectively and to avoid "false alarms" which waste money and reduce the likelihood that people will react to future warn- ings. The flood warning system was considered in Reaches 4, 5, and 6 where there are significant numbers of structures that receive flood damage. Enforcement of floodplain regulations is assumed to be a part of all of the alternatives considered in this Master Plan, however, floodplain regulations cannot reduce the potential for flood damages to existing structures. Relocation of Channels to New Alignments This alternative involves abandoning the existing channel and relocating the channel river to a new location. The relocated channel would be engineered to reduce or eliminate flood and erosion problems. The disadvantage of this alternative is that it requires extensive right-of-way and a relatively 1 arge capital expenditure. Channel relocation was not considered in Reaches 1 through 7. In Reach 8 relocation of the channel is part of the gravel mining operations and general plan for river stabilization. Measures such as floodproofing and flood warnings can reduce the vulner- ability of exiscing structures. In Reach 4 the industrial/warehouse type buildings are particularly suitable for floodproofing because they generally have first floor elevations several feet above the street, and because of the lack of openings below the first floor. Other Alternatives Other alternatives include levees, dams, and other approaches not included above. These other alternatives were not considered in any of the reaches except in Reach 8 where several large floodplain lakes were evaluated. The large floodplain lakes alternative was dismissed after discussions with Adams County personnel due to the significant concerns over unresolved safe- ty, water quality and water rights issues. While fail-safe dams could be built for the large lakes, they would be too costly for the private gravel operations. The State of Colorado has recently authorized the State Engineer to operate a satellite system for monitoring river flows. This satellite system will initially be used for the purpose of forecasting flows for the administra- tion of water rights within the state. In the future, it will be possible to also use this system for the purpose of providing flood warnings by increasing the number of gaging stations monitored and developing a computer system to predict flood peaks. Currently there are no formal flood warning systems in place on the South Platte River itself. Warnings are provided on a regional basis by the National Weather Service, but these forecasts gen- erolly do not contain specific predictions of flood heights, peaks, or times of peaks. Because flooding on the South Platte can occur as the result of intense thunderstorms over tributary basins in the metropolitan area, these A failure of an upstream lake embankment could result in a flood surge which would propagate downstream causing failure of subsequent embankments. This domino effect could result in the river flowing on bedrock through Adams County and present significant difficulties in downstream reaches of the South Platte River. Even without the embankment failures, the sediment trapping nature of the lakes would affect downstream reaches. Water quality issues have been presented in Section VI of this study. Water rights issues, including storage rights and evaporation losses, could require substantial effort to reconcile. It was felt by the consultants