1904.] HAUPT — THE MISSISSIPPI RIVER PROBLEM. 87 



tions are : (i) That they raise the flood heights ; (2) that they break 

 too easily and often ; (3) that they cost too much ; (4) that they 

 cause the river bed to rise, because they do not permit the escape of 

 sediment over the banks.'' 



Moreover, it is important to note that the physical conditions 

 attendant upon the drainage basin of the Po are wholly distinct 

 from those of the Mississippi, since the Alpine tributaries with 

 their steep decline of over a mile in twenty are checked and regu- 

 lated by the magnificent and extensive storage and sedimentary 

 basins of Lakes Maggiore, Como, Iseo and Gorda, from which the 

 effluent issues comparatively clear and flows 340 miles to the sea, 

 which is about 1260 feet below. The total basin drained by the 

 Po covers but 27,000 square miles, while its mean discharge at the 

 mouth is only 60,745 cubic feet, or about one-eleventh that of the 

 Mississippi. 



The benefit of the lakes- as sediment basins is in part neutral- 

 ized by the formation of pools in the bed of the stream, for the 

 levees do not hug the banks closely but are in places miles apart, 

 and they have been '* so spaced at and near the mouths of important 

 tributaries that the major bed forms a sort of reservoir, in which is 

 stored not only the floods but still — and to disappear with time — 

 the deposits carried by the affluents." 



This disappearance takes place by the receding stage distributing 

 the bars along the bed of the stream, thus causing elevation, as in 

 the Mississippi, where similar pools are found to exist ; so that, not- 

 withstanding the great reservoirs on the tributaries of the Po, the 

 defective alignment of the levees has aggravated the shoaling and 

 bed elevation, as shown by the record. 



But aside from general observations, the greatest weight should 

 be given to the carefully conducted surveys made by the Mississippi 

 River Commission, covering a reach of two hundred miles from the 

 mouth of the Arkansas river to Vicksburg, and made at an interval 

 of about twelve years, for the purpose of determining this question. 

 The composite cross-sections of this reach show a fouling of the 

 low-water channel to the extent of about four feet, and an enlarge- 

 ment of the area between low and high water amounting to nearly 

 17,000 square feet, due to the increased caving of the banks from 

 the efforts of the augmented volume to enlarge its bed. This 

 amounts to not less than 206,200,000 cubic yards of eroded mate- 

 rial per annum in the reach of seven hundred and fifty miles from 



