6 BULLETI^Sr 198, U. S. DEPAKTMENT OF AGRICULTUEE. 



periods after the streams themselves have returned to a normal 

 stage. A similar condition occurs when the land is flooded by back- 

 water coming through the levee gap from the river. The land being 

 lower than the banks of the streams, a large area is left covered with 

 water, which disappears very slowly. 



THE SURVEY. 



Base level lines were run along the railroads and cross-level lines 

 were run on all east and west section lines. All bayous and water 

 courses were meandered and channel sections were taken where 

 needed; in many cases levels were carried with the meanders. A 

 base level line was carried through Lincoln County on the main hne 

 of the St. Louis, Iron Mountain & Southern Railway, and some 

 cross-level lines were run in this county as aids in the determmation 

 of the topography of the watershed. A reconnaissance of Lincoln 

 County was also made. The levels were tied to precise level bench 

 marks at Arkansas City, Trippe Junction, Walnut Lake, and Varner.^ 



Bench marks ^ were set approximately one-haK mile apart on the 

 level lines. Usually these were root bench marks, the trunk of the 

 tree being blazed and the number of the bench mark inscribed. 

 These were set as near as practicable to section and quarter section 

 corners. 



Soil borings were taken on the main ditch lines, and these borings, 

 showing the character of soil encountered, are indicated on the 

 profiles (fig. 6, in pocket at end of bulletin). 



Gauging stations were established at various points over the district, 

 and daily records kept of the gauge readings. The highest water- 

 surface elevations observed are shown in figure 2. Current meter 

 measurements were begun in March, 1912, during the heavy rains, 

 but it was impossible to continue them, owing to the backwater from 

 the Mississippi River, which flowed through the gap in the levee. 

 The boundary of the flooded area (fig. 2), due to inflow through this 

 gap, was obtained by personal observations and was checked by 

 the gauge heights as furnished by the gauge readers. 



THE DRAINAGE PROBLEM. 



The water from which the district must be protected comes from 

 two sources; first, direct precipitation upon the watershed in which 

 the district lies, and second, overflow from the Mississippi River, 



1 The descriptions and elevations of these bench marks were obtained from U. S. Geological Survey 

 Professional Paper No. 46 (1906). That publication states that the elevations of these bench marks are 

 referred to mean Gulf datum, but since the conclusion of the survey it has been foimd that these elevations 

 had been corrected by a small constant. The results obtained from ties made to the Misssissippi River 

 Commission bench marks show that 7.35 feet should be subtracted from Memphis datum elevations in 

 order to reduce them to the datum used in this survey. 



2 A list of the bench marks set, with their elevations, locations, and descriptions, is on file with Drainage 

 Investigations, United States Department of Agriculture. 



