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property owner as technical information for their implementation, or if supported by the local community, the Congress, and the President, it may lead to Federal implementation. A second justification for Federal consideration of nonstructural measures is that, if the Federal Government uses public funds to investigate means to solve public problems, it should investigate all means provided they are within the general study authority set forth by Congress. Existing/Future Development Measures which are designed to control flood waters - reservoirs, levees, channel modifications, diversions - protect both existing and future flood plain development. For nonstructural measures, however, some measures are designed. principally for existing structures, some only for future, and some for both. Relocating a structure off the flood plain, for example, is intended for existing structures; flood plain regulation, on the other hand, is principally for future development. Keeping water out of a basement which is already built is quite a different problem from designing and constructing a new structure to do the same thing. Existing structures pose special problems because they are already built and use patterns have been established. Also, there is often uncertainty regarding the nature of the materials and workmanship used to construct the structure and of its present condition. This is an important question if it is desired to keep water out and subject it to hydrostatic loads. When this uncertainty exists either the measure is not used or it is used conservatively. Also, there is usually less flexibility in applying nonstructural measures to existing as opposed to new structures. Aesthetics, lot lines, elevations, and zoning, are all established and must be modified and the desirability to do so may be a significant factor in implementing the measure. Traditionally, flood control planning has focused on protecting existing structures because authorizations were made in response to floods which had recently caused damage to existing structures. The need to protect these structures will continue, but, in addition, there is a need to give equal attention to future development. While future land enhancement was sometimes a part of a protection plan it was usually secondary and limited. Much of our flood plain land is undeveloped and federal policy mandates that we encourage wise use of this land. Nonstructural measures are particularly suited for this task. Thus, in planning with these measures the distinction between existing and future development should be recognized and the appropriate measure or measures investigated for each. Costs Since nonstructural measures can be used for individual and small numbers of structures or for small acreage of land their investment cost can be quite low. Most structural measures on the other hand are normally large scale and have a large investment cost. This is not to say that for a given level of protection the cost per structure is any greater or less with one type measure or the other, this would have to be evaluated on a project by project basis. Rather it says that because nonstructural measures can be used on a very small scale the first costs can also be small making it especially attractive in situations where investment capital is limited. Measures which allow a wide range of first costs may have a better opportunity for implementation than those which have a comparatively high first cost. Being able to invest at several levels also encourages a variety of investors. The Federal Government may be willing to relocate several hundred structures at a cost of several million dollars; a community using grant money may opt for relocating ten or twenty structures for several hundred thousand; or a homeowner may choose to raise his structure for several thousand. Nonstructural formulation allows this flexibility. 6