434 BEroin of office of expeiument stations. 



prevents tlio p;rowth of weeds, brush, ami other ve<];etation that 

 woiilil furnish shelter to the many burrowing animals which, ordi- 

 narily, occasion much annoyance and also damajjje to the levees. 

 The sudtlen rise of outside waters often endaiifj^ers lovees on account of 

 the increased seepage at such times, which is probal)ly often due rather 

 to the more porous nature of tiie soil above the ordinary water level 

 than to the increased head. Such floods, however, develop all weak 

 spots caused by muskrat holes and the like. When a failure occurs 

 from this cause the outer end of the break should be immediately 

 closed by a few shovelfuls of clay, planks, or sacks of earth, and a 

 trench then dug across the levee. The tunnel made by the animal 

 can then be filled with puddled clay and the damage thus remedied. 



CANAL SYSTEMS. 



• 



Where a plantation does not adjoin a bayou or other good outlet, it 

 is often necessary to construct outfall canals for some distance, often 

 through heavy timber, which, of course, greatl}^ increases the cost 

 of the reclamation work and calls for the cooperation of a number 

 of landowners in order to make the plan feasible. These outfall 

 canals, as well as those surrounding the levees, furnish good means 

 of transportation by boat, and often the flow of water from the 

 drainage plant will be sufficient to keep them scoured out, so that they 

 require little attention. Such transportation routes, connecting, as 

 they do, with a series of lakes, bayous, and streams, place the various 

 plantations in a comparatively independent attitude, so, even though 

 not furnished with convenient railroad facilities, they are still within 

 easy and convenient reach of good markets. Plate XVIII, figure 1, 

 shows such a canal constructed as an outlet for two drainage dis- 

 tricts. The small canal shown forms the reser\^oir of one of these 

 districts and, as shown by Plate XVIII, figure 2, it has been cut off 

 from the outfall canal by an earth dam and the pumping plant, as 

 appears, is in process of erection. Along the banks of these canals 

 willows and cottonwoods, brush and weeds often grow, but as they 

 are above water level they do not, as a rule, ofl'er much interference 

 to the flow of the stream. Another growth, however, that causes a 

 great amount of annoyance and in some cases practically stops the 

 flow of the water in the ditches is the water hyacinth, which is known 

 locally as a lily. It is practically impossible to navigate through these 

 obstructions, w^hen once well established, except by the use of stern- 

 wheel power boats. These plants, introduced from abroad, have 

 rapidly spread through many of the southern streams, so that means 

 for checking their growth or eradicating them entirely are eagerly 

 sought. Plate XVII, figure 2, page 422, shows a canal filled with 

 these water hyacinths which have grown to about 18 inches above 

 the water surface. The view shows the main discharge canal of a 



