12 BULLETIN 304, TJ. S. DEPARTMENT OF AGRICULTURE. 



enter the river channel. Plate I shows hydraulic-fill levees during 

 construction and after completion. The completed levee shown has 

 a top width of about 8 feet, side slopes of 3 to 1, and a height of 

 12 to 15 feet. Plate II shows a levee constructed by a drag-line 

 excavator. 



As in the construction of any other structure, the foundation of a 

 levee is the prime consideration. Unless the material in the founda- 

 tion is suitable, and unless proper precautions are taken, the levee 

 may fail in spite of the best of construction work on the levee itself- 

 Insufficient care in preparing the foundation for levees has been the 

 most frequent cause of subsequent disaster. Before constructing 

 the levee, the entire area to be occupied by it should be cleared of 

 all vegetation, and all stumps and roots to a depth of 4 feet should be 

 grubbed up. The entire surface should then be plowed, with a large 

 dead furrow in the center. This treatment may suffice if the material 

 in the base is firm and dense, if the levee is only moderately high, and 

 if the water will not stand against the levee for more than a few days 

 at a time. If, however, the material in the base is not of the best, 

 or if the levee is more than 10 feet high, or if the water in the river 

 will remain against the levee for periods longer than 10 days at a 

 time, a muck ditch should always be dug along the center line of the 

 levee. This ditch should be at least 3 feet deep in any case, and 

 always deep enough to cut off any possible seepage. It should be 

 at least 3 feet wide on the bottom and be filled with the best material 

 obtainable, preferably a clayey mixture well compacted. No 

 vegetable matter should be permitted in any of the material used 

 to form the levee. If the subsoil in the borrow pits is clay, this 

 material should be placed in the center of the levee to form a con- 

 tinuous core wall from the muck ditch upward to the top of the 

 levee. The top soil, being thus placed on the slopes of the levee, 

 will facilitate the growth of grass. 



MAINTENANCE. 



The care of levees subsequent to their completion is an important 

 matter too often neglected. The slopes should be smoothed and as 

 soon as practicable a good growth of grass should be secured. For 

 this purpose bluegrass, Bermuda grass, redtop, timothy, and clover 

 are all used. A good growth of sod will hold the soil in place and 

 prevent erosion. A mowing machine can be used on a 3 to 1 slope, 

 but scarcely on a steeper slope. On a steeper slope, too, beating rains 

 are likely slowly to wash out the soil and thus gradually reduce the 

 height of the cross section. All weeds and brush on a levee should 

 be cut at least twice during the growing season, as they are par- 

 ticularly harmful, loosening and disintegrating the soil by their 

 roots. Sometimes the top of a levee is used as a road, but this 

 practice is not to be commended, for the wagon wheels cut off the 



