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I I I I I I I I I I I I I I I I I I I Chapter 2 CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS The following conclusions were derived from Phase A and Phase B of the drainageway planning study. These general findings are based on field investigations, hydrologic and hydraulic studies, and, when appropriate, an economic analysis of the benefits and costs associated with alternative flood cont~ol measures. Specific recommendations for each of the four basins in the study area are given in the next section. FLOODING PROBLEMS The study area should not experience any major flood damage even during the 100-year storm. The flooding problems are mostly associated with erosion, "backup" waters from restricted road crossings, damages to homes and contents from ponded water, and collection of mud and debris. Maintenance of the drainage facilities is needed to assure their full capacity is available to carry flood waters. HYDROLOGY The watershed is not yet developed to its projected land use. For hydrologic purposes, the basin is considered ultimately developed. Runoff under fully developed conditions should not be significantly larger than current runoff from the existing level of development. Duration of peak flood flows is very short. with their short distances cause the runoff quickly. The extent of damages is lessened duration of flooding. The steep basins to be removed by this short GENERAL DESIGN CONSIDERATIONS underground conduits have a small benefit-cost ratio. Although these facilities can provide major flood protection, their costs are very high. However, installing underground conduits is desirable to adjacent property owners because it removes the drainageway from their backyards. Channel regrading or grass-lined channels with drop structures (as required to reduce velocity) and removal of restrictions at road crossings are the most acceptable solutions to all entities and the least costly means of providing reduced flood damages and multi-use projects. 2-1