DEAIKAGE OP WET LANDS OF SOUTHERN LOUISIANA. 29 



Levees. 



The front or northeast levee on this tract is located on ground about 2 feet 

 above average tide. As the storm tide in this place is only about 2.5 feet above 

 mean tide, the front levee is very small, perhaps 2 feet high and having a bot- 

 tom width of 5 feet. Along the outside of this levee is a small diversion ditch 

 designed to carry the water draining from the higher land in front across to 

 the commercial canal on the side of the tract. Owing to the small size of the 

 levee and also to the fact that it was built by hand, considerable seepage water 

 finds it way into the front part of the district. The trouble from this source is 

 noticeable only when the tide stands about a foot above mean height for any 

 great length of time. Along the other three sides of the tract it was necessary 

 to construct a levee varying in height from 3 feet at the front to 6 feet at the 

 back along Lake Fields. Along this portion the present crown of the levee is 

 about 5 feet wide, with a bottom width of about 35 feet. This would give a side 

 slope of about 2i to 1. 



The levee along the north and south sides not only is in good condition, but 

 it seems to allow about the minimum amount of seepage during ordinary stages 

 of outside water, although there is no berm between the levee and the outside 

 canal. There is no lateral ditch on the inside* of the levee nearer than about 

 180 feet, so that the actual difference of the water levels inside and outside 

 of the district is rarely greater than 4 feet, and usually about 3 feet. While 

 the percentage of muck in this levee is small, there seems to be a rather con- 

 tinuous layer of muck in the base. At ordinary stages of water there is no 

 great seepage through this layer of material, but during December, 1911, and 

 January, 1912, when the tide level of the outside water was for nearly one 

 month li feet above mean level, the seepage was very noticeable, and the pumps 

 were kept in operation a much longer time than when removing the run-off of 

 rainfall only. This levee was built with a dipper dredge, and no muck ditch 

 was cut in the base. It now appears that the falling earth did not penetrate 

 the layer of muck and form a bond with the underlying silt. The seepage was 

 so great on some parts of the levee during the above-mentioned period of high 

 water that a ditch was cut along the middle of the levee for some 300 or 400 

 feet, and refilled with a dipper dredge. This method of refilling gave better 

 results than that of hand filling and tamping, and rendered quite impervious 

 the part of the levee so treated. The levee needs similar treatment for its 

 entire length. The levee along the back or southwestern side of this district 

 was built under conditions somewhat different from those attending the con- 

 struction of the levees on the other three sides, this levee being located in the 

 open watei- in the lake. The material placed in this levee was very soft, so 

 that a number of layers were added before final completion. It was started in 

 1907, and the last addition was made in 1910. At first this levee was badly 

 situated, as on the outside there was a canal having a depth of 6 feet, and im- 

 mediately on the inside, with no berm between, was a reservoir canal with a 

 depth of about 10 feet. The width of the levee at the level of the outside water 

 was 35 feet, and more or less seepage occurred when the lake stood above its 

 usual level for any length of time. At such times the head of water on the 

 levee frequently was 7 or 8 feet. This seepage seemed to take place through 

 defective spots in the body of the levee rather than through the base, for it 

 was only when the water was above mean height for a considerable time that 



^ The side of a levee on which the protected land lies is termed the " inside." 



