The engineer is continually battling against the titanic might of the Mississippi River. The problem has proved too formidable for local effort, and its solution is reorganization under national control
AN UNEXPECTED FLOOD of exceptional severity which threatened to engulf the works of the power plant at Keokuk, Iowa, on the Mississippi. An embankment of timbers, stone, earth and sandbags was built out across the river to protect a cofferdam while foundations were being secured. The sudden flood threatened to demolish embankment and cofferdam. The embankment had to be heightened with sandbags and the cofferdam strengthened. Men had to place these bags on a wall two feet wide, with water dashing over their feet and the wind blowing with hurricane force.
ONE of the greatest internal engineering problems confronting the American nation is how to keep the Mississippi River in check. The Mississippi and its tributaries drain some 1,250,000 square miles of country, nearly one-third of the area of the United States. After the disastrous floods in the early part of 1937 the Federal Government was petitioned to take over the sole control of the mighty but erratic stream and its great tributaries. Hitherto the problem had been largely left to the States bordering the river; these States had been aided in the work by Government grants and by help from U.S. Army engineers. The control of the Mississippi and its tributaries, however, is now recognized as a national problem, and one which only a central government, and a wealthy one at that, can satisfactorily solve.
Only those acquainted with the Mississippi and its power to wreck cities and devastate large tracts of fertile land can grasp the seriousness of the situation and the great problem it presents. Ever since towns began to rise upon its banks, and steamers to ply upon its waters, the engineer has been at war with the Mississippi. He has lined its channel with 2,500 miles of dikes or levees, and has established at various points protective works and plant, so that when floods occur men and material can be hastened to the place of attack and prevent the rising waters from submerging the surrounding country.
The story of man’s settlement upon the Mississippi is one long record of stern fights against the forces of Nature. Between 1874 and 1937 there were no fewer than eighteen disastrous floods in the Mississippi Valley. Scarcely a year passes without one of more of its many tributaries overflowing its banks and causing widespread damage. The value of property destroyed in these floods amounts to several hundred millions of pounds, and many thousands of lives have been lost. Fertile districts as large as Ireland, with cotton, sugar, fruits and Indian corn under cultivation, have been suddenly swamped, and large towns have been inundated.
These misfortunes have not been due solely to the river rising to a great height, overflowing its banks, and then gradually subsiding into its original channel. That is too conventional for the Mississippi, which is nothing if not original in its methods. It has a disconcerting knack at times of suddenly changing its course. Important towns, whose existence depends upon their trade with the river, suddenly find themselves stranded several miles inland. This happened to Vicksburg. That city used to be on the river, and boasted of miles of wharves and docks. Now it is five miles distant, on Centennial Lake.
The river seems to delight in falsifying the maps and making geography to suit itself. The town of Delta, for instance, formerly stood above Vicksburg; now it is several miles below. The place itself has not moved, but the sportive Mississippi has shifted its course, so that it now runs past Vicksburg before it reaches Delta. The great stream is all twists and turns, and is constantly breaking through from one curve to another. Sometimes this has the effect of reversing the flow through the channel for a mile or two, which means that dwellers upon its banks wake up one morning to find that the river which has been running east past their doors now runs in the opposite direction. In dealing with the flood problem of the Mississippi, the engineer has to take into consideration not only the Mississippi River itself, but also the great tributaries that feed it. In the floods of January and February 1937, when nearly a million people were rendered homeless and many towns were submerged under several feet of water, it was the Ohio River that had overflowed. This river is 960 miles long and joins the Mississippi at Cairo (Illinois). The Mississippi River has its source in a lake in Minnesota, 1,680 feet above sea level, and it flows southwards for a distance of 2,620 miles to the Gulf of Mexico. At St. Louis (Missouri), however, the Mississippi is joined by the Missouri River, rising in the Rocky Mountains 2,910 miles distant by the flow of the stream.
The Mississippi and the Missouri are regarded virtually as one stream, one of the greatest waterways in the world, with a total length of 4,500 miles. The average discharge of the Mississippi River at the mouth of the Red River, its last great affluent, is 610,000 cubic feet of water a second. In times of severe flood the discharge has been as high as 2,300,000 cubic feet a second.
The quantity of sediment brought down by the river is immense. Careful tests have shown that it amounts to a carload of silt every second, or, in six months, a quantity equal to the total excavation made for the Panama Canal, namely 210,000,000 cubic yards. This silt furnishes the river with plenty of material for its geographical experiments, and it is continually creating sandbars and building new banks, to the confusion of navigators and pilots.
At present the principal method of defence is the levee. To the average individual a levee means a dike which holds off water, and nothing more. A Mississippi levee, however, is a clever piece of engineering work, upon which is expended much care and skill. In this flood-troubled country levee-building has been brought to a science, and carefully studied for the past two hundred years. M. Le Blond de la Tour, a French engineer, built the first levee, a mile long, in front of the infant city of New Orleans in 1717. Now there are 2,500 miles of them.
A sum of £46,000,000 has been spent upon levees, and they have called for 243,000,000 cubic yards of material. The levees protect from overflow some forty million acres of the most fertile lands in the world, situated in the heart of a great continent and sustaining a population of several million people. They vary from 10 to 40 feet in height, and have bases from 80 to 250 feet wide. The larger ones are mountain ranges in miniature.
Patrolled Day and Night
The levees are built much in the same way as railway embankments, by contractors’ equipment of locomotives and cars, operating over temporary tracks, or by various special levee machines. The most notable type of levee machine is the big dredge, which transfers dirt in great cartfuls from the riverside to the top of the dike. Then there is the travelling scoop, hauled on a wire cable, which gathers material from distances impossible to a dredge and deposits it neatly on the top of the bank.
Some of these levees are close to the river; others are set back a mile or more away from the stream. Thus in flood time the stream in places is from two to three miles wide. Each year the levees have risen higher and higher, yet the Mississippi, objecting to being thwarted, keeps piercing them or overlapping their crests. They are built entirely of earth; not a stone or stick goes into a levee. Stones and sticks are said to make the embankment porous, and the creation of a filter is the last thing to be desired.
THE MISSISSIPPI VALLEY, which has long been subject to violent and devastating floods. At Cairo (Illinois) the Mississippi is joined by the Ohio River, one of its great tributaries. At St. Louis (Missouri) the Missouri River, which rises in the Rocky Mountains, nearly 3,000 miles away, joins the Mississippi. The Missouri and the Mississippi are generally regarded as one stream — one of the greatest waterways in the world — with a length of 4,500 miles.
The greatest enemies of the levee are the crayfish and musk-rat. These pests attack the bank from the river side, boring into the earth either straight through or perhaps tortuously. The holes thus made spurt water directly the river reaches their level. If allowed to remain unattended they will increase in size until they undermine the entire embankment.
Directly the river begins to rise the levees are patrolled day and night by armed guards. As the waters climb up the banks the farmers whose plantations border the stream become anxious. A break on one side of the river would instantly relieve the danger for miles on the other side. To save his broad acres, a farmer may be tempted to use a little dynamite across the river: hence the presence of the guards.
The levee, however, is not the only device used for controlling this erratic stream; Where the river flows between banks of soft sand, easily washed away, the banks are strengthened with giant mats, fashioned as follows. Barges loaded with willow saplings are towed to the spot to be protected, and scores of workmen are then set to work to weave an enormous mat from them. As it is woven the mat is allowed to float upon the water, and it is added to until it is. some 1,000 feet long by 250 feet wide. Wire cables are then strung under it to keep it on the surface, and heavy stones are placed evenly upon it in the “cribs” provided. When this has been done the wire cables are released, and the great stone-laden mat sinks uniformly into place, extending from the water-level towards the bottom of the river, in the manner of a great rock curtain. These “revetments”, as they are technically called, cost from £5 to £6 a foot, and if the bends where “cave-ins” occur could all be treated in this way the channel would remain permanent.
Government Snag Boats
In other places the banks are protected with stone paving, and even with concrete. To cut the banks down to a gentle slope before the paving is laid, powerful streams of water from hydraulic jets are requisitioned. With such terrific force does the water strike the banks that it eats them away, and it is computed that a single jet will do the work of a hundred navvies.
In the lower reaches of the river, because of the immense quantities of sand carried down by the current, dredgers have to be used to prevent the formation of sandbanks. The dredgers are fitted with a powerful “suction rake” capable of raising no less than a hundred tons of sand a minute. One of the chief drawbacks to navigation in the Mississippi is its many bars, or crossings, as the pilots call them. They are virtually great ridges of sand, and there are forty-three of them between Cairo and the Gulf of Mexico. They come up close to the surface at times of low water, sometimes within four or five feet. On the tops of them lie dead trees brought down by floods and anchored by their matted roots. These derelict trees are called “snags”, and so numerous are they that a fleet of snag-boats is maintained by the Government to remove them so that navigation shall not be obstructed.
PRECAUTIONARY MEASURES in action at Gayoso Bend revetment, near Carruthersville (Missouri). Some 400 men were at work in September 1936 on the sinking of a huge articulated concrete mattress. Such methods as this are used to protect banks of soft sand, which might easily be washed away by flood waters.
As the river passes through great stretches of wooded country, and is frequently in flood, hundreds of trees are carried down every year. It is a common occurrence for trees 30 to 50 feet in length, with roots 20 feet in diameter, to be hauled out of the bed of the stream. This is the work of the snag-boats. These flat-bottomed craft, with their long overhanging arms, are so built that they can navigate in exceptionally shallow water. With their massive chains and powerful engines they haul the trunks out of the stream. Among their crew of thirty officers and men are a number of divers, for it sometimes happens that a snag is so firmly embedded that it is impossible to move it. Divers are then sent down to place dynamite in holes in the trunk, and the obstruction is blown up. When raised the snags are sawn into short, harmless lengths and then sunk in deep water.
The Mississippi always gives warning before beginning one of its outbreaks. Once the ultimatum has been delivered, however, it knows no rules or laws, and shows itself a relentless foe. After the heavy rains in the spring the river always begins to rise —sometimes slowly, at other times more rapidly. A Mississippi flood below Cairo is curiously deliberate and leisurely. Sometimes the crest of the stream, within the levees, makes from thirty to fifty miles a day. At other times it makes not more than ten or fifteen miles a day. Again, the river may rise to a certain height, then fall somewhat; then rise even higher. Occasionally, therefore, the exact location of the flood crest is' temporarily lost.
As soon as a rise in the river is announced the engineers get busy at the forty-three levee stations scattered along the stream. Armed guards are sent to patrol the embankments, and all the principal cities and towns are advised of the coming floods. The river gauges are anxiously consulted, and thousands of men are concentrated and held in readiness to beat off the threatened attack.
As the waters climb higher and higher, sandbags are placed upon the tops of the levees. Should a leakage be detected at any spot, a box of raw pine, 40 feet deep, is immediately dumped into the river, made fast to the bank, and then filled with bags of dirt or sand. For this work everyone available is requisitioned, since if the leak is not immediately stopped a crevasse will form, and then nothing will prevent the river from breaking through. Sometimes the battle is over in a few hours; at other times it is waged for weeks.
Entire City Submerged
The floods of the Ohio Valley of January and February 1937 were among the worst experienced so far. Nearly a million people were rendered homeless, over a thousand lost their lives, and the damage to property was estimated at £100,000,000. Both the Mississippi and the Ohio rivers rose far above normal flood level. The Ohio was the worse offender. Its waters reached a height of 68 feet, or 16 feet above normal flood level. Every town and settlement along its banks, from Pittsburgh to Cairo, at the confluence with the Mississippi, was called upon to wage a stern battle against the ever-rising waters.
Army engineers directed the fight, and thousands of convicts were brought from the prisons and put to work upon the levees. Every able-bodied man was pressed into service, filling sand-bags, taking cartloads of earth to the levees, or erecting barricades at weak spots to save homes and cities from the dreaded waters. Men toiled till they dropped from exhaustion. Despite these herculean efforts the river broke through the levees in several places.
A portion of Pittsburgh, known as the “Golden Triangle” because it contains the high-class shopping, amusement and financial district of the city, was submerged. The citizens of Cincinnati (Ohio) put up a great fight to save their city ; but the river won, and the streets of the city were flooded to a depth of 12 feet. A similar fate overtook Louisville (Kentucky), Evansville (Indiana) and Frankfort (Kentucky), as well as other settlements along the banks of the river.
As the waters threatened to shatter the flood wall at Portsmouth (Ohio), which was a 60-feet concrete structure built at a cost of £200,000, it was decided to open the sluices and allow the water to submerge the city. This was regarded as the lesser of the two evils. The wall had been built to protect the city against floods after the terrible experiences of 1913. The entire population of the city — 30,000 in all — was evacuated at 3 o’clock one morning to the sound of sirens. Then the water poured in and submerged the streets to a depth of six feet. The population took refuge on hills behind the city.
GRADING A BANK OF THE MISSISSIPPI at Gayoso Bend revetment (Missouri). In some places the river banks are protected with stone paving or with concrete, and before such protection can be laid the banks must be cut down to a gentle slope. In other instances, where immense quantities of sand have been deposited by the current, dredgers have to be used to prevent the formation of sandbanks.
Fourteen out of the seventy square miles of the city of Cincinnati, where 30,000 people lived, were submerged by the flood waters. While this evacuation work was going on and the resources of the authorities were taxed to the utmost, the air was rent by a tremendous explosion, followed by a great mass of flame hundreds of feet in height. Fifteen tanks containing a million gallons of petrol had suddenly ignited. The refinery and the flood waters immediately surrounding it became a bed of flame. It was feared that the blazing petrol would be carried by the flood waters through the city. The flames spread over an area of four miles by half a mile. A hundred prisoners were released from the city gaol to help fight the flames. A girl telephone operator in a factory near the refinery saved many lives by shouting a general warning through the house telephones.
Meanwhile the cities in the Lower Mississippi Valley, from Cairo down to the Gulf, were experiencing an anxious time. The Mississippi itself was in flood. This meant that the Mississippi was unable to take the flood waters of the Ohio as rapidly as if its own flow had been normal. When these great rivers are in flood they turn part of their waters into the mouths of their tributaries, producing backwater. If this backwater gets high enough, it breaks over the banks and levees of the tributaries. The engineer has to give his attention not merely to the main stream, but to the tributaries as well. Thousands of workers under army engineers were sent to strengthen and protect the levees along the Mississippi to meet the oncoming flood waters from the Ohio, more particularly along the three hundred miles stretch of the river between Cairo and Memphis (Tennessee). So serious was the situation at one time that the Government made arrangements for the evacuation of half a million people.
Drinking Water Contaminated
In the neighbourhood of Memphis 200 camps were formed and goods trains, lorries, motor coaches and thousands of private cars were waiting at various points, ready to carry the people away. Although the flood water did overtop the levees at Certain points, the evacuation was fortunately not necessary. Had not vast quantities of the flood water escaped through broken levees in the Ohio Valley, the evacuation of the towns in the lower Mississippi would no doubt have been necessary.
In addition to fighting flood waters, the authorities are concerned with another problem which is equally important and is often as strenuous. This is the work of the Red Cross and Public Health Service. Their task is a colossal one. First, communication has to be re-established with the stricken area. Hundreds of thousands of refugees have to be sought out, fed, clothed, and inoculated against disease. When floods occur men, women, and children, with their domestic animals, hasten to the levees, to ridges or to ancient Indian mounds in their endeavour to escape the rising waters. Crawling up from the flood come foxes, rabbits, quail, deer and wild turkeys, to climb over man’s piled-up furniture, bedding, and bundles, unmindful now of him and his dog. Only the snake is denied shelter. Some people take refuge up trees, in the upper stories of their dwellings and on roof tops. These have to be rescued by boat.
The biggest task which faces the authorities as the flood recedes is fighting fever, smallpox and pestilence. In the floods of January and February 1937 over 60,000 people were inoculated against disease and 25,000,000 grains of quinine were distributed. More than 20,000 dead animals — mules, horses, and sheep — were destroyed, cartloads of oil being used to burn the carcasses.
THE FULL FURY OF THE RIVER released by blasting the levees near Cairo (Illinois). In a final effort to save that city from the flood waters in January 1937 the engineers, despite resistance from local farmers, blew up the levees and flooded 131,000 acres of rich farm land. Such drastic measures often have to be used when the situation becomes serious.
As the water subsides people move back by the thousand to see the condition of their homes. Here drinking water is contaminated. Whole villages under water for days and perhaps for weeks reek with decaying plant and animal life. Flowing water gives way to stagnant pools, strewn with floating things black with flies. Mosquitoes breed by the million. Only the most rigid precautions and the strictest adherence to health and sanitation principles can avoid an outbreak of pestilence in the months ahead.
The floods vary considerably in their intensity. That of 1927 was particularly severe. In the Lower Mississippi Valley 18,268,780 acres of land were completely flooded. Over 800,000 people were driven from their homes, 313 lives were lost, and the damage to property totalled £60,000,000. The river rose 24 feet above normal and, to save New Orleans, levees were blown up by dynamite. New Orleans is a walled city. Levees form its walls; without them the river would engulf it, for it lies lower than the river. Every drop of rain that falls in the city and all its sewage have to be pumped up and out of it.
In the Mississippi floods of 1913 seventy-four steel bridges were entirely destroyed or made unsafe for the passage of trains. The restoration of these bridges presented no mean engineering problem. In 1903 Kansas City experienced a terrible flood, when the whole business district of the town was inundated. The flood drowned out railway yards and stations, stockyards, packing-houses and other large business concerns. In the main street the water was 25 feet deep. Fifteen of the city’s bridges were swept away by the flood.
The removal of this wreckage from the river after the flood had subsided proved a formidable task. The masses of wrecked steel became so firmly interlocked that they had to be blown asunder by dynamite and the broken pieces lifted from the river bed by powerful cranes mounted on improvised barges. A year later, long before the city had fully repaired the damage done by this flood, it experienced another, fortunately not so serious, and again in 1908 and 1909.
Local Levee Boards
Engineers declare that these disastrous floods of the Mississippi can be controlled, but that it is an engineering project of the first magnitude. It would cost, they say, between £50,000,000 and £75,000,000. The defences would take the form of increasing the height of the present levees and strengthening and extending them. Subsidiary channels would be created here and there to control the overflow, and huge reservoirs would be formed by the building of dams and floodgates in the tributary rivers. By this means the surplus flood waters could be held up and released as opportunity offered. Congress is fully aware of the situation. In 1879 it created the Mississippi River Commission. This sits at St Louis. It is made up of army engineers and civilians. Its task is to control the river as best it can. Each year Congress votes funds for its use. Moreover, from Cape Girardeau (Missouri) down to New Orleans taxpayers along the river are grouped into local levee boards. There are twenty-eight of these boards. They are affiliated with the head office at Memphis. Their union is called the Mississippi Flood Control Association. It seeks to work in harmony with the official Mississippi River Commission.
Each levee district has its local problem. It is, however, the River Commission which decides when, where and how levee work shall be done. For each £2 spent by the Federal Government in any district the local levee board must spend £1. Because local boards have sometimes failed to raise their share, needed work has been left undone. Hence, as a levee resembles a chain in that the whole is no stronger than its weakest part, the levee system as a whole is defective. Every one is agreed that the time has come for the Government to step in, make a thorough study of the greatest American river, and subjugate its vagaries.
THE GREAT PROTECTING WALL at Cairo, Illinois, which was built in 1936. Its position at the confluence of the Ohio and the Mississippi places the city of Cairo in considerable danger when either river is in flood. In the terrible floods of 1937 the Ohio was the chief offender, and rose to a height of 16 feet above the normal flood level.
Some of these levees are close to the river; others are set back a mile or more away from the stream. Thus in flood time the stream in places is from two to three miles wide. Each year the levees have risen higher and higher, yet the Mississippi, objecting to being thwarted, keeps piercing them or overlapping their crests. They are built entirely of earth; not a stone or stick goes into a levee. Stones and sticks are said to make the embankment porous, and the creation of a filter is the last thing to be desired.
