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Can Floods Be Prevented?

Chris Wilkins/AFP/Getty Images

The flood in the Mississippi Valley is one of the great disasters in our history. From 6,000,000 to 7,000,000 acres are in the region affected, the population of which is at least 350,000 persons. Of these, some two-thirds have been evacuated to refugee camps, and the other third remains living precariously in the upper stories of houses, or camping out on knolls, inadequately sheltered and menaced by starvation and epidemic. The number of dead will never be known exactly, but is at least 300; and the damage to property is estimated at various amounts from $200,000,000 up. Since a great part of this comes from the pockets of poor people who have lost all they have in the world, the work of rehabilitation will require huge sums, which are not now in sight. Fields must be replanted, cattle and work animals replaced, houses repaired or substitutes built, roads reconstructed. This money must be provided, either by private charity or through a federal appropriation which, if it is to be made soon enough to be of any use, will require a special session of Congress.

It is only natural that people should be asking whether such disasters as this are in fact preventable. On this point, it can be said definitely that the measures taken in the past have certainly been inadequate. These have consisted almost exclusively of building levees, on which about $168,- 000,000 has been spent by the federal government since 1879. Every time a bad flood has occurred—and they have come at an average interval of only six years—the levees have been built higher. Yet almost every time, the next flood has broken through or has gone over the top of the dike. This has been true of the three great floods of recent years: those of 1912, 1922 and 1927. It is inevitable that people should begin to ask whether the federal and state authorities, who are pinning all their hopes to the levee system, are not making a mistake—whether their attempt at a cure does not in reality aggravate the disease?

Before the coming of the white man, the Mississippi frequently overflowed its banks, in the regions near its mouth. A vast area went under water temporarily, with the melting of the snows in the north and the coming of the spring rains. Not only was this true, but the river had its own "spillways^" or extra outlets to the sea, through which the surplus water ran off. The struggle with the river in the past century, and particularly since 1879, has been a record of continuing attempts to reclaim lands in the flood area. The natural spillways have been cut off. The levees, of which there are now 2,500 miles, have been built ever higher and stronger. The fight to narrow the area which is subject to flood has been a successful one. Yet it stands to reason that if the same amount of water is made to follow a narrower course it will run in a stream proportionately deeper. A small part of this added depth will be accounted for by the scouring effect which the more rapid current will have upon the main channel; but most of it will be represented in the form of increased depth of water with corresponding likelihood that the levees will be broken or submerged. This would be true, even where the volume of water the same as in former years. But there is, unfortunately, the best of reason to believe that the volume of water in flood times has been enormously augmented as a result of the short-sighted policy pursued in the northern states.

Such a flood as we are now experiencing takes place when we have heavy rain, or rapid melting of snow, or both, throughout a large part of the 1,200,000 square miles of the Mississippi Valley. That has been the case this year, and in every preceding year of high water. However, before the Valley had been settled, there were several factors, operating to hold back the flood waters, which are no longer so effective as they once were. Along the western slopes of the Appalachians, where the Ohio and its tributaries rise, there were extensive forests. In several ways these served to retard the creation of torrents of water. The air above a forest is cooler, producing frequent slight precipitation instead of an occasional deluge. The fall of the water is slackened by its striking the leaves and by the necessity for its working through the spongy mass of dead vegetable matter which covers and interpenetrates the top layer of the soil. The roots hold the earth together and prevent its-.washing down into gullies which form a convenient channel for the flood current.

Further to the west, where most of the countryside consisted of open plains, the margins of rivers were heavily wooded, and this timber served the same purpose as the forests. The plains, before they had been broken by the plow, were covered with a rich, heavily matted vegetation. Even the most torrential rains were unable to get through to the roots, loosen the soil and wash it away. There were, moreover, numerous swamps and marshy places which acted as natural reservoirs in periods of excessive precipitation, holding the waters until they drained off slowly in the course of weeks, or evaporated. Finally, there were many lakes, which also caught and 'impounded much of the surplus water.

Most of the lakes are still in existence, of course; but all the other conditions have been radically altered. The greater part of the forest has been cut away, not on the European system which removes only a small part of the standing timber each year, allowing natural growth to replace it, but by stripping off practically every stick, leaving only the bare hillsides. This process has been accelerated by our failure to prevent disastrous forest fires. Much of the timber along the banks of streams has also been cut. The virgin sod has, of course, been plowed. In our eager search for farmland, we have drained the swamps and even some of the lakes. We put in ditches and sewers, in order that the water may run off as fast as it falls. Our municipalities are particularly proud of their fine storm drains.

What is the result? According to such authorities as Professor J. Russell Smith of Columbia University, author of "North America," E. A. Sherman of the U. S. Forest Service, and H. H. Bennett of the U. S. Bureau of Soils, our careless refusal to take any thought for the future has not only greatly augmented the seriousness of the present flood, and made it certain that similar disasters may be expected at frequent intervals in the future, but is resulting in wearing away the precious and practically irreplaceable topsoil from much of our best lands. As Mr. Bennett observes:

Failure to hold the absorptive surface soil of fields and pastures against the denudation of erosion has contributed to a much more rapid removal of the water that falls upon those eroded lands. The mellow topsoil that is gone was far more retentive of moisture than the comparatively impervious subsoil that sheet erosion has left behind. .. . If this kind of soil wastage is not stopped, there is little likelihood that floods will be controlled. Practically nothing is being done about this phase of flood prevention. There are no hillside terraces north of the Arkansas River. Eighteen inches of topsoil has been removed from the youthful fields in some parts of northeastern Kansas. The entire topsoil is gone from hundreds of thousands of acres in western Virginia, western Pennsylvania, eastern Kentucky and southeastern Ohio. From these lands rain water courses much faster to the Mississippi than formerly. Terraces and grass woodlots, forests, and other soil binding and soil-building crops will vastly improve the flood situation; not only will they slow up the runoff of water, but they will save the most valuable part of the soil and will reduce the clogging of streams which cuts down their carrying capacity, and adds to the flood danger.

The Department of Agriculture has Issued a brief list of measures which it urges as a means of flood prevention:

The general reduction of soil erosion to prevent rapid runoff and .the clogging of streams. [Several rivers, formerly navigable, have been filled with silt in a few years' time and can no longer be used.]

Largely increased efforts by the states and federal government and private owners for cooperative forest fire control.

Largely increased programs for public forests on tributary headwaters, both by the federal and state governments. A much larger program of tree planting on denuded forest lands.

Encouragement of farmers and other land-owners, through state and federal aid, to plant trees, on rough lands and along water courses.

A study of the possibilities of restoring some of the bottom lands to their original condition as carriers of flood waters and producers of forests and game.

The only other important proposal looking to the future is one which comes from former Governor Gifford Pinchot of Pennsylvania, who was for many years chief of the Forestry Service of the United States. Mr. Pinchot believes that the flood waters could and should be impounded to some extent behind dams on the upper reaches of the tributary streams, and released in small amounts over a period of months. He points out that, by this system, not only could the flood conditions be much ameliorated, but enormous quantities of hydroelectric power could be produced—sufficient, in fact, to pay for the whole cost of the enterprise.

If our analysis of the situation is correct, how does it happen that so little has been heard of anything except levees and more levees, in the past? One reason is, of course, that the worst sufferers from the floods have not been those in areas where (deforestation has taken place, but those along the lower reaches of the river, visited by the accumulated flood waters from the Mississippi and its great tributaries. A levee is a simple and visible object, behind which people may rest secure in a confidence which is justified—most of the time. No one's vested interest is upset by the building of a dike; while on the other band, every alternative method of flood control means the impairment of somebody's economic interest. Spillways render useless vast tracts of arable land. So do reservoirs and the use of low-lying regions for catch basins. Timber men get enormously enhanced profits by destroying forests instead of trimming them out: in fact, they are probably correct when they plead that no one who pursues a careful system of arboriculture can compete in the open market witb tbose who are taking off all the timber in one operation. Owners of drained swamps would fight to the death any proposal for restoring them to their first condition. The farmer insists on his right to plant the most profitable crops, even though he may be subjecting bis lands to an erosion which will make them useless in another hundred years. That is something for posterity to worry about; and "wbat bas posterity ever done for us?"

It is necessary to keep a perspective in considering this subject. Even witb all tbe barm tbat bas been done, we still go through five years out of every six without a flood; and if all the points in the program of the Department of Agriculture were carried out, we should still in all probability suffer an occasional visitation. Yet it should be clear tbat tbe problem by which we are confronted is enormously greater than is believed by those simple souls who sbout for bigger and stronger levees, and are at present the only voices which make themselves beard in the balls of Congress. On October 1, 1927, the Mississippi River Commission is to make a special report on flood prevention. The Special Spillways Board is also to report, at the same date. It may be possible, while the memory of the present disaster is still fresh, to build up a body of public opinion in favor of remedies which are not, like the levees, in the long run a mere aggravation of the malady.