Flooding in the Basin
The subject of floods is fraught with more drama than that of water shortages, for a flood can be not only a hardship but a catastrophe. For this reason, accounts of floods tend sometimes toward exaggeration, and appeals and proposals for protection against flood threats often take on the highpitched tones of impending disaster. The subject badly needs sober public understanding, despite the fact that for decades a good many knowledgeable scientists and engineers and planners have been laying out their conclusions for general perusal.
Rivers are supposed to run out of their banks occasionally. Topographically, stream flood plains—the expanses of flat bottomland that have been deposited over long periods of geological time by the streams they border—are similar to what legal terminology calls "attractive nuisances." Men have always known that they were dangerous and yet have always utilized them to some degree, because they contain the best farm land, are convenient to water, and are easier places in which to build houses and factories and roads than are the safer hills and uplands.
In times before engineering technology was able to erect such effective control structures as today, populations who had lived along "flashy" watercourses long enough to learn their habits tended to build their more valuable structures back away from the parts of the flood plain that got wet most often, leaving those parts for cropland and timber, or sometimes for shacktown, promenades, and parks. Thus long-settled countries and regions have often developed through trial and error a degree of what is now called "passive flood protection," which simply means recognizing that the flood plain is sometimes a rather perilous place, and treating it accordingly. It was valid in past ages, and it is still valid today.
The Potomac Basin has been inhabited by civilized men since long before modern engineering evolved. Possibly early town-builders' wariness of floods contributed to the fact that the problem of flood damages here, though quite real, is somewhat less severe than in certain other sections of the nation. At specific points of concentrated flood plain development—Petersburg, W. Va., on the South Branch; Cumberland, Md., and the areas upstream from it on the North Branch; and metropolitan Washington at the head of the estuary—figures show significant amounts of average annual destruction by rampaging stream waters. In headwater areas or small urban watersheds scattered throughout the Basin, there are a number of other places where some damage takes place, whether agricultural or structural. The total average annual damages for the Basin, as computed in the 1963 Army Report, amount to about $8.6 million.
Along small streams, whether urban or rural, the same principles apply as along large ones, and the proper protective measures are similar if smaller in scale. Leaving the worst parts of the flood plain in fields or parks is the usual and effective form of passive protection. Where existing development demands structural measures, it has been common practice to cover streams over as sewers or to confine them to straightened concrete channels that sluice rainwater and mud away as fast as they will flow—though often this is not fast enough, as is shown by occasional messy and costly overflows of Four Mile Run between Arlington and Alexandria. And the loss of pleasant brooks and creeks through such practices is a heavy price to pay.
More and more often lately in such cases, a combination of some passive protection with the small headwater dams that "catch the water where it falls" and soil conservation measures to protect the watershed lands above the reservoirs, has proved to be a better solution. This is what has been done in the Rock Creek watershed in the District of Columbia and Montgomery County, Md., and its value was shown during the heavy rains of September 1966. Here stream valley parks have given passive protection for a long tune, though the popularity and heavy use of the parks have caused a big investment in picnic areas, playgrounds, and other facilities, which themselves have often suffered expensive flood damages. As a result of long effort by a watershed association, two S. C. S. dams had been finished shortly before the September flood at the only useful sites on the creek's upper branches that rapidly spreading residential development had left available. They kept runoff from the big sudden rains entirely in hand in Maryland and reduced damage in the Federal park in the District to a point far below what it would have been without them.
Ideally, of course, such planning should be done before heavy development, and a pilot urban watershed program of this sort is being undertaken in the Pohick Creek basin on the metropolitan fringe in Fairfax County, Virginia. With freedom to locate necessary structures in the right places and to protect them against silt and ruinous runoff by requiring good land treatment and a sensible distribution of buildings, pavements, and wooded or grassy open space, planners there ought to get good flood protection while preserving a pretty valley and stream for the people who will be living in the neighborhood. From any number of standpoints, this is vastly preferable to the more usual traditional procedure of letting growth run wild and then trying to cope with trouble when it comes up.
The headwater dams are equally effective in reducing flood damages in small rural watersheds where losses warrant their installation. But even on a massive scale of installation they have little influence on downstream flooding along the main rivers. In such places—at Cumberland, Petersburg, and the Washington metropolis, and at certain other river towns where less damage occurs—other measures are going to have to be selected and applied in each individual case according to costs and benefits, physical possibilities, and the best interests of the region.
Cumberland and the lesser damage centers on the North Branch are scheduled for the classic engineering solution of big dams upstream. The existing Savage River reservoir, finished in 1950, has cut down flooding notably in that area, and a dam at Bloomington above Westernport, already authorized by Congress, will relieve it still more, as well as fitting into the complex clean-up task along the North Branch and furnishing water for local and Washington use.
The 1963 plan proposed similar protection for metropolitan Washington and for Petersburg, West Virginia, in the form of major reservoirs at Seneca and Royal Glen. Physically and culturally, there is very little similarity between the two communities, but their flood situations and the potential effects of the proposed protective structures have a certain kinship.
At both places there has been development of the flood plain, with the result that damages occur when the communities' respective rivers get out of their banks. In relation to its size—around 2000 people—Petersburg is subject to much heavier trouble of this sort than the metropolis. It sits near the head of the lovely narrow farming valley through which the main downstream South Branch flows, a few miles below the point where two principal forks of the river join after rushing out of the mountains. In June of 1949, a flood there claimed five lives around Petersburg and three at Moorefield downriver, where still another main fork comes in, and wrought major destruction through the neighborhood.
The 1963 Army Report calculated Petersburg's average annual flood damages at over $200,000, and advocated construction of a $30 million, multipurpose reservoir at Royal Glen just upstream from Petersburg, to do away with most of the damage and to permit further industrial development of the flood plain, as well as to provide a great deal of water for downstream use and for regional recreation. People and groups in the area with interests standing to benefit from the reservoir were naturally in favor of it. Under present Federal policy—which will be mentioned again—its flood-protective function would cost them nothing, whereas levees or other locally effective approaches would demand a good deal of local effort and outlay, besides disrupting the town's aspect and its relationship to the river.
Opposition developed also. The very name of Royal Glen suggests the scenic qualities of the country roundabout. As at Seneca, a dam here would flood out some country with unique scenic and recreational values, including the famous Smoke Hole Gorge down which the clean South Branch runs between steep mountains dotted with caves and flavored with the quiet simplicity of the life that isolated hill folk lived there up into modern times. It is a section much appreciated by whitewater canoeists and hikers and horsemen and others from that region and elsewhere, who care about rugged and unspoiled places. Despite its remoteness, the proposal that it be inundated aroused more vigorously hostile comment among conservationists and nature lovers in general than perhaps any other item in the Army program except Seneca. The State of West Virginia declared itself opposed to the project, and to date has maintained that position.
Again like Seneca, the Royal Glen site does have certain unique advantages for use as a reservoir. But, as at Seneca also, its functional virtues do not appear to be nearly so unique as those of the scenery and natural values whose obliteration would be a heavy part of the reservoir's price. In 1965, the immense scenic value of a large part of the country it would wipe out was recognized by its inclusion in the big Spruce Knob-Seneca Rocks National Recreation Area. It is strongly to be hoped that that recognition is never withdrawn.
The issue of scenic destruction at both Royal Glen and Seneca tends to obscure another set of even more basically relevant considerations having to do with the whole question of flood plain occupancy and use, the extent to which those who benefit from it should share the cost of such protection as may be necessary, and possible ways of reversing a present trend toward inexorably larger national flood damages each year despite ever larger and more expensive structural protective measures at public expense.
THE HYDROLOGIC CYCLE
It is a complex subject that can only be summarized here. What it amounts to is that America has strayed too far from the ancient hard-won wisdom of treating flood plains with respect. It has been lulled by the achievements of engineering, encouraged by a general absence of inadequacy of State and local planning that takes such matters into account, and conditioned to a set of Federal laws and policies piece-built over a long period of time, with consequent inequities, imbalances, and loopholes that tend to emphasize structural protection at Federal expense for indiscriminate flood plain development. The result has been a neglect of the possibilities of flood plain management, which undoubtedly in the long run—as in the long past—will prove to be the most valuable tool for reducing these damages, for it will bring about a restriction on ill-advised and uneconomic encroachment in these streamside areas.
The reason most such encroachment is bad, with or without a dam upstream, with or without levees, is that it establishes the certainty of further and larger flood damages in the future, with the certainty of further and larger expenditures to combat them. It has been pointed out that no such thing really exists as flood control, but only a given degree of flood protection. Economics and technology dictate that reservoir capacities devoted to the storage of flood water, for example, be considerably smaller than the maximum runoff conceivably possible. This means that sooner or later there is going to be a great flood against which the reservoir or reservoirs will not suffice. If the reservoirs' presence, as is most often the case, has directly encouraged a lot of flood plain speculation and construction downstream, then the great flood is going to do more damage than was ever done before, and more reservoirs and other protective measures, most often Federally financed, are going to be demanded, at a price that rises sharply as less desirable sites and methods have to be employed, and with frequently catastrophic scenic effects. These considerations apply to small watersheds as well as large ones.
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.
Interestingly, certain floods to which Washington is susceptible can be partially guarded against only by such approaches as the ones mentioned above, and not at all by upstream dams. One of them occurred in August of 1933, when a hurricane pushed the water in the estuary upstream and raised it to flood stage at the capital.
