« AnkstesnisTęsti »
And his disgust is much intensified when the location of the line of the levee anticipates and greatly enlarges the encroachments of the river. If his front is, for example, a mile, building the new levee will involve the loss of at least one hundred and sixty acres of his best land, for, in a caving bend, the new line is rarely placed nearer the old one than a quarter of a mile, and if, out of abundant caution, it should be located still farther back, the loss is increased in proportion; for all land outside the levee becomes as valueless for planting purposes as if already careering in suspension toward the Gulf of Mexico. The proprietor, grieving over his prospective loss of land, is recalcitrant; he cannot be made to understand why so large a margin is necessary; he fights against it as long and as hard as he can, and even resorts to chancery suits and injunctions.
Besides the opposition, active or passive, of local interests, there were weighty considerations moving the levee authorities to a moderate policy. Anxious as they might be to put the public money where it would last the longest, there was no absolute certainty that it was necessary to place the levee so very far from the bank. The river is nothing if not capricious; the caving bank of one season is often perfectly solid the next; on this point the prognosis of the oldest inhabitant is of as little worth as that of the latest arrival. One thing was certain -the farther from the river a levee may be built, the more it will cost. A pure scientist, authorized to draw upon unlimited funds, might disregard such considerations, but they had much weight with practical business men whose objects were, first, present immunity from overflow, and, second, such permanent reclamation as was attainable with the means at their command.
When levees were built en amateur by planters, the methods were less scientific and the work far less effective than later, when they became the business of civil engineers and Irishmen. The received idea of a levee, for a long time, was an embankment sloping from the surface, at an angle of even forty-five degrees, to a line a foot or two above high-water mark. It was usually made by casting with the spade from each side, so that in front and rear, close to the base of the levee, was an irregular trench two spades deep, usually full of water from which the earth had been taken. There was no "seep-water" ditch, and whenever the river stood against the levee, the " transpira
tion water" which oozed through it filled the trench along the line of the levee, and rendered any work upon it in case of storm or other emergency a matter of great difficulty. The levee was built on the natural earth; stumps and even logs were often left in it-a cause of much peril, as the earth, in settling, would shrink away from the wood and leave a cavity, which the insinuating water soon enlarged to dangerous proportions. Now and then a root-hole just below the surface would form the primordium of a crevasse, and sometimes the levee, being on and in no degree incorporated with the earth upon which it rested, would slide bodily away and let in the importunate river. That such structures should have resisted any water, not to say a “big water," could only be regarded as a fortunate accident.
The mode of building a levee which superseded the primitive style just described is this: The space which it is to occupy is first carefully cleaned off; trees, roots, stumps, logs, weeds, even grass and leaves, are removed. Then in the middle of the space, extending longitudinally the whole length of the proposed work, is dug a ditch three feet wide and three feet deep, which is to be straightway filled up again. This is called a mock-ditch, or, as some people say, a "muck-ditch," but why "muck" is one of the things that has not yet been found out. The object of this is twofoldto close all root-holes and to mortise the superstructure into the natural earth, thus preventing any sliding under the pressure of the water. As the levee is built of loose earth, its mass coalesces with the loose earth with which the mock-ditch was filled, and when the levee has been completed and settled it forms, with the contents of the mock-ditch, a homogeneous mass anchored three feet all along the line in the solid ground. The next process is to build the levee. The material is to be taken only from the outside or side next to the river, and should not be cut nearer than twenty feet from the base of the levee; the earth is carried in wheelbarrows upon runplank. The dimensions of levees have varied from time to time, according to the amount of funds available for their construction. In any case, the top of the levee should be three feet perpendicular above high-water mark; the base line should be five, six, or seven feet, according to the ratio in force, for every foot of perpendic ular height; the top should be level, and
as broad as the levee is high. Thus where | high-water mark is four feet above the level of the natural bank, the perpendicular height of the levee should be seven feet, the breadth at the top should be seven feet and its thickness at the bottom thirty-five feet, forty-two feet, or forty-nine feet, as the ratio of five to one, six to one, or seven to one might be in force. Taking, for illustration, a seven-foot levee constructed upon this last ratio, it will be observed that, with the water standing four feet deep, there will be on a horizontal line twenty-five feet of solid earth between the surface of the water outside and the air inside, and fortynine feet between the bottom of the water without and the air at the natural surface of the earth within.
tober until the river, by rising out of its banks in the spring, shall serve notices to quit. The laborers, collected by the contractors in St. Louis, Cincinnati, or Cairo, are chiefly Irish, with a few English and Scotch, an occasional German or Scandinavian, and rarely a native American. When the season closes, all except a few who have been employed as ditchers return to the upper country, and the swamp knows "the Irish" no more until the fall. Levee work is paid for by the cubic yard, usually twentyfive to thirty-five cents per yard. The payment is made in money or its current equivalent in levee bonds, which are cashed either directly by tax-payers or by brokers who buy them to sell to tax-payers. The cost of levees varies, of course, with their dimensions; a good seven-foot levee with ample base would cost from eight thousand dollars to eleven thousand dollars per mile, higher levees costing in a much greater and lower in a much less proportion. height of levees varies with the relative elevation of the bank, ranging from five to thirteen feet in perpendicular height, averaging perhaps nine or possibly ten feet.
The season of peril to levees is variable, ranging from the first of April to the first of July. I have known a levee broken by equinoctial storms about the 20th of March, but usually the evil day comes later. It depends greatly upon the weather in the upper country: a mild winter brings an early "water"; a hard winter, keeping the rivers long closed with ice, delays the coming of the floods. There is a general impression that heavy snows above portend and produce very high water in the Mississippi. This is a mistake; snow is not formidable because there is very little water in it, as anybody can discover by melting a cupful, and because it usually passes away gradually unless dissolved by heavy rains; in that case, it is the rain that does the mischief. A kindred delusion prevails that the floods in the Mississippi are caused by the melting of snows on the plains and in the Rocky Mountains. To this source is due only what is known as the " June rise," but it is usually so late that it has no coadjutors, and of itself is rarely formidable. It is, besides, so gradual that, even when superimposed upon a pretty full river, it adds little to the height of the water though much to its duration.
The last but indispensable step in the process of levee-building is the "seep-water" ditch, which is dug some thirty or forty feet from the inner margin of the levee, and parallel with it. The function of this ditch is to receive and conduct away the seepwater, or transpiration-water, which oozes in considerable quantities through even the most compact of levees. If permitted to remain it would render the ground about the inner base of the levee intolerably muddy, and would operate as a great disadvantage in case of emergency. The seep-water ditch must be connected with plantation ditches or otherwise put into communication with the swamp in the rear, so that the water can be carried away. Finally, as a finishing touch to the new levee, it should be planted with Bermuda grass. If tufts of this grass be set two or three feet apart all over the surface of the levee it will, in a year or two, cover it completely with a very dense sod, and by its interlacing roots add materially to its waterresisting capacity. When water stands for a long time against a levee, the current and the waves seriously abrade its surface, cutting in sometimes so deep that an inopportune wind-storm would assuredly break it. A heavy coat of Bermuda sod is a very efficient preventive of this kind of disaster. I have seen, at the end of a long period of high water, a piece of levee deeply indented all along the line, and, in some places, cut more than half through, while adjoining it a strip of Bermuda-covered levee, subject to the same exposure to wave, wind, and current, which had not, apparently, lost a pound of earth or a tuft of grass.
The levee-building season lasts from Oc
The most dangerous floods come from the Ohio and its affluents. When all these up to the "head of the hollow" conspire
and do their wickedest, the aggregate of water is enormous and the result is a long season of suspense, anxiety, labor, and peril. The upper Mississippi and Missouri with their tributaries are not capable of equal mischief. Usually there is a succession of high waters; and the result is that during the whole critical season, April, May, June, the river is generally bank-full, and often stands against the levee in a most threatening attitude for three, four, five, or six weeks together. At high stages the Mississippi falls very slowly, and as a rise travels much more rapidly than a fall, the rivers relieve each other in keeping up the water. The Arkansas is sui generis; it rises very rapidly, and several times in the course of a season an immense flood comes down, rushing with great velocity quite across the Mississippi, dyeing the turbid yellow waters with its peculiar red for a hundred miles below. Whenever its boom coincides with a very high stage of the Mississippi, disagreeable things are likely to happen almost anywhere from its mouth to Vicksburg.
It must not be supposed that an overflow is always as universal and disastrous as that of 1844. When the general line of levee stands firm, and there are only a few crevasses, each has its own area of devastation limited by the topographical configuration of the country. All land back from the river is lower than that upon its margin,
but there is no little diversity in the relative depression of these lower levels. The lagoons are lowest, then the cypress brake, the open swamp, the green-brier ridge, the switch-cane ridge. All these are lower by three to ten feet than the cane ridge of the interior, which is itself lower than the land on the margin of the river. Where there is a bayou the land on one side or both is relatively high. Some bayous were originally outlets from the river, and were filled up at their heads either by deposits before the reclamation era or by levees since. Other bayous are the outlets of the larger lakes, such as were portions of the bed of the river, and in most instances the banks of the lakes are comparatively high and communicate by ground of similar elevation with the margin of the river. Thus, at irregular intervals all along the banks of the Mississippi, are strips of higher ground, extending in a measure parallel with the general course of the river for a great distance. As a sort of inchoate natural levees, they divide the country into a number of sections partially independent of one another in the matter of protection from inundation. If a crevasse takes place below one of these natural breakwaters, the lands above it are comparatively safe. As long as there remains within reach of the errant flood a space adequate to the receipt and discharge of the volume of water admitted by the
crevasse, the higher levels are not invaded. If, however, the break takes place above the ridge the security is not so perfect, because of the normal tendency downward of the water; but it often happens that the natural elevation of the ridge, especially if reënforced by a volunteer side levee, protects the plantations below, throws off the water, compels it to disport itself in the open swamp and deep cypress-brakes of the interior, and to seek through the usual outlets of the swamp a pass-way to its ultimate destination.
In the immediate vicinity of a crevasse the action of the water upon the land is direct, flowing over it with great velocity toward the lower levels of the swamp, spreading, of course, on either side. In its rapid descent it often cuts holes in places, and elsewhere covers spots of considerable extent with sand a foot or more deep. In 1846 I saw large patches of this character, white as the sands of Florida, barren as Sahara, the souvenirs of 1844. In time the winds dispersed the sands in some measure, and persistent and very deep plowing partially restored the fertility of the soil. The great body of overflowed lands, however, is differently affected; the water, having filled the adjacent swamps, and unable to find adequate outlets into still lower depths, backs up on the higher lands and quietly takes possession, continuing to rise until it has reached the highest level it can attain with the volume imparted by the crevasse. Thus, at a short distance below and a fortiori above a crevasse, the highest ground, usually alongside the levee, remains for a long time and often altogether untouched by the water.
The width of a crevasse varying from a hundred feet to half a mile or more depends upon the height of the water above the surface of the earth, the slope in the rear, and the tenacity of the soil of which the levee is composed. As the space afforded by the breach for the escape of the water increases, the abrading force operating upon the levee diminishes, and when it falls below the cohesive strength of the material of the levee the abrasion ceases. Sometimes the work of destruction is limited by securing the ends of the broken levee (this is effected by driving down heavy stakes and depositing masses of gunny-bags filled with earth), and sometimes the same result takes place when the critical point is masked by a thicket of willows, or cotton-wood, or even a fortuitous drift-log.
Closing a crevasse becomes practicable when its current has been so far diminished by a fall of the river without, or the rising of the overflow water within, that stakes can be driven with good hope that they will remain where they have been placed. The difficulty is that, as the width is diminished by the operation, the velocity of the current is increased, and up to the very last it is uncertain whether the break can be closed at all; contrary to the proverb, it is here the last step that costs. This process is, except perhaps in Louisiana, less frequently attempted than it should be It is not a very easy thing, of course; the cost is considerable, the result always problematical; it may be wholly superfluous, for the river may retire within its banks so that the levee can be rebuilt after the ordinary fashion. On the other hand, the river may not recedemay indeed rise so high that the operation will be utterly impracticable; in view of that probability it is wise to seize the opportunity to close the crevasse while it can be done, and save to the community perhaps hundreds of thousands of dollars. Under favorable circumstances very useful work is sometimes done with apparently inadequate means. I once saw a crevasse three or four hundred yards wide, where water was running through from two and a half to three feet deep, closed in five or six hours by sixty men operating with a dozen skiffs, a row-boat, a lot of stakes, and a supply of gunny-bags.
The amount of damage inflicted by an overflow varies greatly; sometimes the fright is the worse result, but generally there is ample and substantial cause for lamentation. Buildings are rarely injured; they might be upset or washed away if a crevasse should occur at a convenient point for that purpose, but somehow levees do not break in front of people's houses. Cattle in considerable numbers are often drowned, but the great damage is the loss of time and the consequent injury to crop prospects. If relief comes in May or early in June, cotton is planted, and a half-crop is a fortunate result. After an overflow, cutworms are especially numerous, active, and malicious, and seldom permit a full stand of any crop to be obtained. If planting becomes practicable later in June, corn only is grown, and that, too, is generally scanty; after the first of July it is hardly worth while to plant anything.
Sometimes, but rarely, the same body of land has suffered an overflow and produced
a full cotton crop the same year. In a certain land in Mississippi, on the first day of April, 1858, everybody was ready to plant cotton, and on that night the levee was broken. It was a bad crevasse, six hundred yards wide and nearly or quite five feet deep, and admitted an immense volume of water. The roar of the rushing torrent could be heard more than a mile in every direction, and the overflow was general and complete. After two weeks the river fell rapidly, and about the twenty-third of the month was well within its banks; another flood, however, was coming, and the river, already under its influence, was beginning again to rise. The levee authorities and the planters interested seized the opportunity, all the hands in the district subject to levee duty were ordered out, two hundred men were put to work, and in five days the breach was closed. The new levee was not a little after the old style, being tall and slender, but experts thought it might survive if the river should not stand against it more than two or three weeks. Whether the Mississippi had permitted it to be built from complaisance or inadvertence will, probably, never be known; it is certain that for two months no reasonable efforts were spared to break it. From the first of May until after the first of July the river stood against it, usually at a high stage, and at one time higher than that which had proved fatal to its predecessor. The people who had had it built and its friends -it had many friends all along down the river, for seventy-five or a hundred miles, who would suffer severely if it should come to grief-were almost in despair; the neighbors sat up with it night after night. Time Time wore on; cotton was growing rapidly; the river stood high upon the very steep slope of the levee; the levee, tough and stanch though a light weight, stood up against the river, each apparently determined to fight it out on that line if it should take all summer. At last the river, beaten for once, retired from the contest, King Cotton was in the ascendant, the elements had been propitious, and, though planted a month later than usual, the crop was a full one. The work of two hundred men for five days in building that inartistic levee saved a cotton crop worth more than a million of dollars.
There are various perils to which levees are exposed during the season of their usefulness, but it must not be supposed that every part of the line is equally in jeopardy
or requires the same kind or degree of attention. Levees built after the more modern fashion, with ample height and base, can usually be trusted to take care of themselves with only a general supervision even when the river stands at high-water mark. Numerous strings, however, not so well constructed or unfortunately located need, during the critical season, constant watching and frequent mending and patching. The dangers are either in the levee itself or its position with reference to the river-bank.
Some old levees are, to speak hyperbolically, "full of craw-fish." These little animals make their way through and come out on the inner side near the base, and in a levee so affected are numerous little round holes an inch or two in diameter, through each of which flows a brisk stream. While the water runs clear there is no danger, but when a craw-fish hole runs muddy water disintegration is taking place in the interior, and at any moment the undermined levee may sink below the water-line and a crevasse may follow. There are two modes of treating craw-fish holes: first, to grope in the water outside the levee till the hole is found, then stop it with a sand-bag or otherwise. This is the best way if the hole can be found; otherwise the surest plan is to build around the inner hole a miniature circular levee rising to the level of the river, and in this, as in a bowl, the water remains tranquil.
Some levees are leaky because of their deficiency in dimensions, others on account of the permeable character of the earth of which they are composed; these are always in danger. Others are in danger because of their exposed position-the wind having a clear sweep for many miles, and hurling water against the embankment during the prevalence of heavy storms.
What to do for an endangered levee depends, of course, upon the circumstances of each particular case. The materials employed are stakes, boards, brush, earth— loose and in gunny-bags. These last, though costly, are in the end the cheapest and best ammunition for " fighting water." They should always be held in readiness and used profusely in cases of emergency.
From what has been said, it is apparent that the protection afforded by the levee system, so far as it has yet been developed, was and is essentially imperfect and precarious. A very grave danger of overflow annually recurs, and the partial security which has been attained is held only by