EECLAIMING OVEEFLOWED LANDS IN MISSISSIPPI, 27 



RELIEF DITCH. 



A relief ditch was then laid out in such a manner that two separate 

 channels could be mauitained the entire length of the bottom below 

 Bywy Creek. Owing to construction limitations the maximum 

 section of this ditch was designed with a bottom width of 100 feet 

 and a depth of flow of 13 feet. With this ditch and with the river 

 channel cleared, the run-off, as computed by the ditch formula, 

 could be cared for above the mouth of Poplar Creek; but from this 

 point downstream it is believed that the relief obtained would not 

 justify the expenditure. The estimated cost of this plan, including 

 the construction of the ditch and the clearing of the old channel, 

 amounted to $27 per acre of land benefited. 



LEVEE AND FLOODWAY PLAN. 



Preliminary computations were then made on a system of protection 

 consisting of levees and floodways. The necessary widths of river 

 floodway and heights of levees were determined. Interior drainage 

 was provided for by ditches with outlets through floodgates to the 

 river channel. The results obtained show that while the cost of the 

 complete system will be high, considering present land values and 

 economic conditions in the district, yet portions of the valley can be 

 reclaimed at a reasonable cost even at the present time, and the 

 remainder can be reclaimed at a later date as conditions justify. 

 Plans and estimates were therefore made along the lines just de- 

 scribed ; these are discussed in some detail in the following pages. 



PROPOSED PLAN. 



The general plan as proposed for the drainage of the Big Black 

 River bottoms consists of: 



(1) The construction of a main ditch and of the necessary laterals 

 at the upper end of the valley. 



(2) The construction of levees. 



(3) The clearing of a floodway through the bottoms, including 

 the present river channel. 



(4) Provision for interior drainage by the construction of ditches 

 and the clearing of present channels. 



The proximity of the river channel to the bluffs or higher land at 

 frequent intervals and the entrance of tributaries into the bottoms 

 divide the ovcrflow(!d land into natural drainage units. From the 

 Mathisti n-Wulthall lloud to Cox Ferry 36 drainage districts have 

 been {)laiiried. These districts, as well as the drainage improvements 

 recommended, are clearly shown, on the accom])anying maps and 

 profiles (figs. 10-12, in pocket at end of bulletin).* 



' For In'lcx map to figure 10, 3eo flguro 2. 



