This costly cycle, which frequently makes the general public pay both in tax money and the sacrifice of amenities to protect the investment of a relatively few who profit from the wrong kind of flood plain use—in plain words, makes the public subsidize their ventures—has established itself widely. In some places, of course, certain kinds of development can take place only on the flood plain, and planning for its structural protection may be amply warranted, with equitable cost-sharing. But the difference between this sort of flood plain use and the much more common, thoughtless, quick-profit type needs to be more widely recognized and established in policies at all levels of government. The subject has been much studied. In August 1966 the findings of a distinguished Task Force on Federal Flood Control Policy, which made detailed recommendations for injecting some sense into the situation, were submitted to the attention of Congress by President Johnson. At the same time, he issued Executive Order 11296 on the subject, directing all Federal executive agencies with influence in such matters to do everything possible to discourage uneconomic and unwarranted use of the nation's flood plains. This, of course, includes the present Potomac planning effort.
FLOOD PLAIN DELINEATION POTOMAC RIVER AT HANCOCK, MD.
At Petersburg, there is little question that the wisest approach to present and future flooding problems would be one that would seek to give reasonable protection to the development already on the flood plain but at the same time deter further construction unless it is floodproofed or houses activities that find a flood plain location so advantageous as to be well worth the risk. In currently available terms, this could be accomplished most feasibly and at the least net expenditure—though not, under present policy, as cheaply to the community itself as by the Royal Glen dam, and not without some notable changes in the town's landscape—by combining a levee system around present development with rigid zoning of the unoccupied part of the flood plain, or its acquisition as parkland.
Another approach that may shortly be possible was suggested by the President's Task Force and is the subject of legislation proposed to Congress by the Department of Housing and Urban Development. Under this legislation, owners of existing flood plain residences and small businesses would be given a chance to buy Federally subsidized insurance against flood damages at reduced rates, while new construction in flood hazard areas would be subject to rates based on the full true risk involved. After 1970, under this proposed legislation, such insurance could be sold only in areas with enforceable codes and ordinances or other measures for sound flood plain management. Such a program could go a long way toward eliminating casual and expensive flood plain clutter, if it were backed up by adjustments in other phases of Federal flood control policy that would similarly place a share of any protective costs where they belong, and hence give an additional strong nudge to citizens and local and state governments to bring the situation into balance.
At Washington, because a high proportion of the flood plain on both shores is in Federal ownership and the use it is put to is determined by Federal agencies, Executive Order 11296 has special relevance in forestalling future increases in the amount of flood damage. Existing damages in the whole urban area are estimated to average $1.4 million each year. The most damaging flood in the metropolis' history occurred in March of 1936, and if a flood of the same dimensions were to strike today, it would cause estimated damages of about $21 million.
These are not small figures, though if they are considered in the light of the area's population and extent and the total value of construction there, they seem less formidable. Obviously the threat of damages of this magnitude must be dealt with, but just as obviously as at Petersburg, the manner chosen for dealing with them should not be allowed to stimulate unwise flood plain construction that would lead to still greater longterm damages.
The Seneca reservoir as proposed in 1963 provided floodwater storage calculated to reduce metropolitan damages by 46 percent. This is a significant though not startling amount of reduction, and it constitutes the most economical one-shot measure of protection that could be attained. However, if the construction of Seneca is precluded for the time being or for good, that measure is not available. Second-best, by Army calculations, would be a combination of several large multipurpose reservoirs on main tributaries farther upstream. But quite aside from other considerations of desirability, these could only be justified economically if a great part of their stored water were destined to furnish massive flow augmentation to ease pollution in the upper estuary. As will be noted in the following chapter, recent studies have raised doubt that such augmentation would be likely to help the estuary nearly as much as had been thought and it is no longer being considered a primary tool for that purpose.
This leaves passive devices and local protection works as the main available instruments for coping with floods at the metropolis. They will probably be most effective if applied in a carefully selected combination of means, with levees and other protective works installed where feasible and desirable, and backed up in other areas by zoning, flood warning systems, and good design including flood-proofing, elevated structures, and similar devices. Some of these principles of design are already being incorporated in new buildings and renewal projects, but the task of planning and locating such things as levees usefully on a flood plain containing a good part of "monumental Washington," the beauty of which is a national concern, is not going to be simple. A good program must be instituted soon, and the extent of the Federal interest in the lands involved should considerably ease the job of coordination.