6 BULLETIN ISl, U. S, DEPARTMENT OF AGPJCITLTUEE. 



Below the Alabama & Vicksburg Railway bridge the river has 

 been declared navigable and the landowners are urging the United 

 States War Department to improve the condition of the channel. 

 There are a great many drifts in this section of the river, and the 

 carrying capacity of the stream undoubtedly would be increased if 

 its conditions were improved. 



No extensive attempts at drainage have been made in the district 

 investigated. One or two property owners have constructed small 

 ditches to drain their fields after the floods have receded, and others 

 have protected small fields by the construction of levees. 



THE SURVEY. 



In making the survey, base levels were first run along the railroads 

 bordering the vaUey. Bench marks were estabhshed at intervals of 

 1 mile or less on railroad mileposts or other convenient objects. 



The flood lines or edges of the overflowed land were located by 

 compass and stadia. Lines of levels were run across the bottoms at 

 intervals of approximately 1 mile, and all of the streams and larger 

 slouehs were meandered. Levels were carried on all of these meander 

 lines and bench marks estabhshed at intervals of approximately 1 

 mile. Cross sections of the streams and sloughs were taken at frequent 

 intervals to determine the sizes and capacities of the channels. 



Soil borings 15 feet deep were taken at intervals of one-half mile 

 on the cross fines in order to ascertain the character of the soil to be 

 encountered in excavation. 



Department bench marks were set near a number of the towns, 

 their locations being shown on the map (fig. 10), and their eleva- 

 tions and locations being given in Appendix I of this report. These 

 bench marks consist of iron pipes, 3 J feet long and 3 inches in diam- 

 eter, set in the ground to a depth of 3 feet. The top of each pipe is 

 covered with a bronze cap on which is stamped "Office Experiment 

 Stations, U. S. Dept. Agr. Drainage" and the elevation of the top of 

 the bench mark to the nearest foot. All bench marks set were of a 

 permanent nature. Those placed on trees were made by cutting a 

 notch in the root and driving in a spike, the elevation being taken 

 on the head of the spike. A few bench marks were estabhshed on 

 bridge piers and tops of culverts. All of these, other than the depart- 

 ment bench marks, are inscribed "U. S. B. M.," followed by the 

 initial of the instrument man and a serial number. Their numbers 

 and location are shown on the map and their elevations may be had 

 by apphcation to Drainage Investigations. All elevations refer to 

 Gulf datum as estabhshed by the United States Geological Survey. 



Very little time was spent in locating land lines, and as the original 

 corners and lines have practically become obliterated it was necessary 

 to tie the survey to loiown objects, such as railroad mileposts, roads, 

 etc. The land lines shown on the map were obtained by adjusting 



