"With the water in the main stream twenty-five feet higher than in the tributary, due to your retaining wall, boy, instead of the water in the Yazoo River flowing into the Mississippi, all the water above the fifty-foot level in the Mississippi would flow into the Yazoo. The Yazoo couldn't hold the water, and as the stream backed up, it would overflow its banks. All the low valleys would be flooded in exactly the same way that they were before, only, instead of the floods coming directly through a break in the levee or over the banks of the Mississippi, they would come over the banks of the Yazoo. That would be true of every small river that flows into the Mississippi, and there are scores of them."
"What can be done, Mr. Levin?"
"There's only one thing to do," the Weather Man answered, "and that's to build up the levee system, year after year, steadily and without pause, making allowances for the tributaries flowing into the Mississippi and paying especial heed to the rainfall that may be expected in the basin. Wherever possible, forestry must be undertaken to keep the slopes from erosion. Reservoirs might be built with great profit, from which water could be let down during the low water periods.
"When the river channels are accurately adjusted to the amount of rainfall in the river basin, destructive floods will be averted. We can never expect that the Mississippi will be absolutely put in harness. The basin is too huge, the amount of water that has to be carried down is too great. Permanent dredging and permanent levee construction and repair will always be necessary, and a close co-ordination between the Weather Bureau and the government and state engineers is a first need in the problem."
"Just how does the Weather Bureau come in," asked Ross, "the rainfall?"
"It isn't only the rainfall of the few days in advance," the Forecaster answered, "it's the rain that has fallen before and the rain that's going to fall. If there should be twelve inches of rainfall after a long drought throughout the Mississippi basin, it would make comparatively little difference, for all the rain that fell on the dry ground would be sucked up by it and only a very little would flow into the rivers and streams that feed the Mississippi.
"On the other hand, if there had been slight but frequent rains for weeks and weeks, those twelve inches of water would make an entirely different story. No one, except the Weather Bureau, would have kept track of the amount of rain that had fallen.
"If the ground has been steadily soaked, even by light occasional showers, twelve inches more of rain cannot soak in. Therefore, the entire amount of rain will flow directly into the stream channels and thus into the Mississippi. Flood warnings will be sent out, the height of the flood crest can be estimated, the length of the period of the danger will be known in advance and the proper preparations can be made. If further rain is threatened, that information can be sent out, also, and the entire Mississippi valley is completely prepared. That's the true preparedness, my boy, being ready for the foe that you know will come. Stupidity or cowardice are the only causes for not being willing and ready to help in time of danger."
