Inundations, Drainage in the City
The following data is extracted from The Creoles of Louisiana.
However, the work done was not without value. It must have emphasized the sanitary necessity for an elaborate artificial drainage of the city's site, and it served to contradict a very prevalent and solicitous outside belief that New Orleans was built on a thin crust of mud, which site might at any moment break through, when towers, spires, and all would ingloriously disappear. The continual alternations of tough clay and loose sand and shells in such variable thicknesses gave a clear illustration of the conditions of Delta soil that favor the undermining of the Mississippi banks and their fall into the river at low stages of water, levees being often carried with them.
These cavings are not generally crevasses. A crevasse is commonly the result of the levee yielding to the pressure of the river's waters, heaped up against it often to the height of ten or fifteen feet above the level of the land. But the caving-in of old levees requires their replacement by new and higher ones on the lower land farther back, and a crevasse often occurs through the weakness of a new levee which is not yet solidified, or whose covering of tough Bermuda turf has not yet grown. The fact is widely familiar, too, that when a craw fish has burrowed in a levee, the water of the river may squirt in and out of this little tunnel, till a section of the levee becomes saturated and softened, and sometimes slides shoreward bodily from its base, and lets in the flood, -roaring, leaping, and tumbling over the rich plantations and down into the swamp behind them, levelling, tearing up, drowning, destroying, and sweeping away as it goes.
New Orleans may be inundated either by a crevasse or by the rise of backwater on its northern side from Lake Pontchartrain. Bayou St. John is but a prehistoric crevasse minus only the artificial levee. A lung-prevailing southeast wind will obstruct the outflow of the lake's waters through the narrow passes by which they commonly reach the Gulf of Mexico, and the rivers and old crevasses emptying into the lake from the north and east will be virtually poured into the streets of New Orleans. A violent storm blowing across Pontchartrain from the north produces the same result. At certain seasons, the shores of river, lake, and canals have to be patrolled day and night to guard the wide, shallow basin in which the city lies from the insidious encroachments of the waters that overhang it on every side.
It is difficult, in a faithful description, to avoid giving an exaggerated idea of these floods. Certainly, large portions of the city are inundated; miles of streets become canals. The waters rise into yards and gardens and then into rooms. Skiffs enter the poor man's parlor and bedroom to bring the morning's milk or to carry away to higher ground his goods and chattels. All manner of loose stuff floats about the streets; the house-cat sits on the gate-post; huge rats come swimming, in mute and loathsome despair, from that house to this one, and are pelted to death from the windows. Even snakes seek the: same asylum. Those who have the choice avoid such districts, and the city has consequently lengthened out awkwardly along the higher grounds down, and especially up, the river shore.
But the town is not ingulfed; life is not endangered; trade goes on in its main districts mostly dry-shod, and the merchant goes and comes between his home and his counting-room as usual in the tinkling street-cars, merely catching glimpses of the water down the cross streets.
The humbler classes, on the other hand, suffer severely. Their gardens and poultry are destroyed, their houses and household goods are damaged; their working days are discounted. The rich and the authorities, having defaulted in the ounce of preventive, come forward with their ineffectual pound of cure; relief committees are formed and skiffs ply back and forth distributing bread to the thus, doubly humbled and doubly damaged poor.
No considerable increase of sickness seems to follow these overflows. They cannot more completely drench so ill-drained a soil than would any long term of rainy weather; but it hardly need be said that neither condition is healthful under a southern sky.
Source: The Creoles of Louisiana