18 BULLETIN 71, U. S. DEPARTMENT OF AGRICULTURE. 



age channels. In this flat country a rise of 3 to 4 feet in the main drainage 

 outlet is a Aery serious matter, and one that demands attention. 



In reclaiming land in this section the usual practice is to inclose the district 

 with levees to keep out the surrounding water ; the drainage water of the land 

 so inclosed is then pumped over the levee into some natural bayou that leads 

 to the Gulf. If the fluctuation in water level in this 6utlet bayou is great, not 

 only is a more expensive pumping plant equipment necessary, but the cost of 

 the levees is very greatly increased. As the usual height of the levees is but 

 from 3 to 5 feet above the ground level of the marsh, a rise of 3 to 4 feet in 

 the outlet bayou will often endanger the levees or at least cause a considerable 

 seepage through them. The danger from seepage is especially great because 

 the fluctuation of the water level takes place very slowly. Thus in the vicinity 

 of the tidal gauge in Bayou La Fourche, near Lockport, the water stood, dur- 

 ing January, 1912, more than 1* feet above mean tide. Districts in this vicinity 

 that were exposed to this tide did a large amount of pumping to set relief from 

 seepage water. 



Up to the present time little attention has been given to the problem of the 

 disposal of the drainage water after it is pumped over the levees. Some sec- 

 tions never will be compelled to give this matter consideration, owing to their 

 favorable locations on or near the Gulf or some other large body of water. On 

 the other hand, there are sections of wet prairie that are isolated from any 

 large bodies of water by distances of from 20 to 75 miles along the shortest 

 natural outlet channel. Thus far few of these districts have experienced any 

 difficulty in getting outlets, for the surrounding limitless prairie is so little 

 above sea level that the drainage water can immediately spread out, and thus 

 causes no trouble. The percentage of land yet reclaimed is so very small that 

 no effect on the carrying capacity of watercourses could yet be expected. 



As the work of reclamation goes forward and district after district is re- 

 claimed, until a considerable portion of the whole area is appropriated, the 

 drainage water when pumped over the levees can not spread over the surround- 

 ing prairie, for the latter will be inclosed by the levees of adjoining districts. 

 The water will then be forced to flow through long winding channels to the 

 Gulf, this distance often being as great as 75 miles. This will mean that the 

 water level on the outside of these interior districts must rise until sufficient 

 head is created to cause a movement of the water to the Gulf, thus greatly 

 increasing the cost of reclamation and rendering unsatisfactory much of the 

 work that is now apparently finished. 



In the planning of gravity drainage districts the common interests of ad- 

 jacent districts in securing good outlet facilities have in all parts of the country 

 long been recognized. Experience has shown cooperation between such dis- 

 tricts to be necessary. As yet, most of the reclamation districts that secure 

 drainage by pumping are independent of each other, and, as pointed out above, 

 those which are fortunately situated will remain so. On the other hand, 

 interior sections will eventually need better outlet facilities to the Gulf if the 

 present policy of developing small independent districts is continued. 



It is evident that the various districts should be so correlated that there will 

 be no interference between the different interests. This makes necessary a 

 general survey of this district, covering the topographic and hydrographic fea- 

 tures. A survey of this scope would show the probable future necessity of in- 

 creasing the present capacity of the natural drainage channels, or perhaps of 

 providing additional outlet channels for some of the more isolated sections. It 

 is quite likely that such additional channels could be used as commercial canals, 

 thus making them doubly valuable. The section of the country lying between 

 Bayous La Fourche aud Terrebonne, in the parishes of the same names, is an 



