| OCR Text |
Show subject to flood. Its application may range through a wide variety of regulations, depending on the de- gree of the hazard and the probable use which might be made of the hazardous area if unrestricted. Minimuna zoning regulations require only a notice of the flood danger. Where the hazard is great, zoning regulations may be applied to exclude build- ings for residential or other uses, and all structures susceptible to flood damage. In some cases, zoning regulations may prescribe methods of building con- struction, and limitations on occupancy and use. As the zoning principle is based on preserving the health, safety, and welfare of a community, its le- gality turns on the police powers of a local govern- mental unit, to preserve the welfare of its citizens. Zoning must be defined in such reasonable terms as may be necessary for that purpose in each locality where it is applied. The primary advantage of flood plain zoning is its low initial cost as compared to the cost of posi- tive flood protection methods. It also has the ad- vantage of preventing slum types of building in areas where the recognized flood hazard precludes construction of a more substantial nature. Also it may be found of value to preserve areas for planned industrial or other higher type of use at the time such uses together with more positive flood protec- tion become economically warranted. An important use of zoning regulations is to pre- vent encroachments on stream channels and flood- ways. Th.e selection of flood control capacity in a reservoir is based in part on the maximum release the downstream channels can carry with safety. A diversion dam or other obstruction could serve to decrease trie channel capacity and impair the reser- voir operation. Floodways riverward of a levee and providing local flood protection should remain unobstructed to carry the flood flows for which the levee heighits were designed. Only flood easements are obtained in the majority of cases, and the right to plan structures in the floodway is not precluded unless clearly made a condition of the easement. Fee-simple ownership of the floodway lands would prevent encroachments. Even under fee- simple ownership by a local agency, laxity or local pressure for a conflicting improvement may allow obstruction_s to be placed in a floodway. A require- ment for establishing and enforcing local zoning regulations could be imposed as a condition of local cooperation in Federal water projects. There are also possible losses from flood plain zoning. A:mong such losses are those due to ex- clusion of more intensive uses which, even after 128 allowing for occasional damage or destruction by floods, may still yield a greater return than the most profitable use under zoning restrictions. The area which would seem a logical place for flood plain zoning restrictions is the Tulare Lake bed. Here periodic flooding from the Kings, Tule, Kaweah, and Kern Rivers has caused severe losses of agri- cultural crops and property. Nevertheless, the soil is so productive that farming is profitable in spite of the flood losses. In cases where the most suitable use under zoning restrictions is not profitable to private enterprise, public purchase may be necessary where institu- tional obstacles stand in the way of profitable alter- native uses; for example, where the area which should be zoned is suitable for agriculture but has been dedicated to urban development. Costs of administering the zoning laws must also be considered. It is possible to evaluate the benefits and costs of a zoning program for comparison with the alterna- tive of providing flood protection. The choice be- tween the two methods of preventing flood damages then turns on the relative economic advantages with due regard for related intangible considerations. Zoning, unless combined with a program for evacu- tion by purchase, restricts future uses and will be most effective alone in a relatively unsettled area. Under certain conditions the combination of limited zoning regulations with partial flood protection might prove the most satisfactory solution of a flood problem. The inadvisability of zoning Tulare Lake bed was mentioned above. It has been found worth while progressively to dike off large areas of the old lake bed and finally to provide measures for complete flood control. Another area which might be con- sidered for application of flood plain zoning is along the American River east of Sacramento. Release for draw-down of Folsom Reservoir will cause pe- riodic overflow in this area because of the limited natural channel capacity at that point. In this case, however, the demand for residential and in- dustrial expansion at Sacramento will probably es- tablish the advisability of protecting the overflow area by levees in order to permit its development and use for those purposes. Conclusions Flood plain zoning has possibilities in the valley as a means to prevent encroachment on stream channels and improved floodways. Other possi- |
