CTPEESS CEEEK DEAIXAGE DISTKICT^ ARKANSAS. 15 



into Lost Chain Creek and thence into Bayou Macon in sec. 32, 

 T. 13 S., R. 2 W. 



Although natural channels have been utilized wherever possible, 

 it was frequently found advisable to locate the ditches entirely inde- 

 pendent of existing streams, on account of the high banks, poor 

 ahgnment, and cost of clearing of the latter. 



Laterals are provided in sufficient number and of such depth as to 

 afford good drainage to the areas lying back from the mains when the 

 necessary field ditches are constructed. 



DETAILS OF DITCHES. 



All of the proposed work is shown in figure 3. Profiles of ditches 

 Xos. 13, 18, 19, 43, 66, 67, 76, and 81 are shown in figure 6 (in pocket 

 at end of bulletin) . Tables of hydrauhc and construction data for each 

 ditch are on file with Drainage Investigations, United States Depart- 

 ment of Agriculture. 



Kutter's formula has been used in aU cases in computing the capaci- 

 ties of the ditches. A roughness coefficient of 0.025 has been used 

 for all artificial channels and of 0.035 for existing channels that are to 

 be cleared. In ditch No. 19, from station 949 to station 976, where 

 the channel of Coon Bayou is to be cleared and grubbed, a coefficient 

 of 0.030 was used. Where practicable, the proposed high-water 

 fines in the channels are placed 1 to 2 feet below the surface of the 

 ground. The grades are made as uniform as practicable, and at 

 points where the grade is decreased, thereby necessitating larger ditch 

 sections, the depth of flow is increased rather than the bottom width, 

 in order to avoid great changes in velocity. 



The minimum ditch planned has a bottom width of 14 feet, side 

 slopes ^ to 1 , and depth of flow 6 feet. This is the smallest that can 

 be constructed economically by a floating dredge in timbered lands. 

 The ^vidth of berm is independent of the width of the ditch, but varies 

 with the depth of excavation. For cuts of 10 feet or less a berm of 

 10 feet is planned; for cuts of 10 to 15 feet a berm of 12 feet; and 

 for cuts deeper than 15 feet a berm of 15 feet is proposed. 



In existing channels whore clearing is the oiily improvement 

 needed all timber and und(Ml)rush should be cut and all debris removed. 

 No stumps should project more than 18 inches above the ground. A 

 short section of ditch No. 19, in Coon Bayou, will need to be cleared 

 and grubb(Hl in ord(!r that it may have the re([uired capacity; in this 

 section aU stumps should he removed or cut level with the ground in 

 addition to the ordinary clearing. 



Tlie widths refjuired as right of way for the ditches were computed 

 by taking three and one-half times the top width of the (hlrh |)lus the 

 width of both berms. The cost of right, of way was estimated at. %2() 

 per acre. No allowance was made for this cost where the ditches fol- 

 low present channels. 



