16 BULLETIN 652, O. S. DEPARTMENT OF AGRICULTURE. 



and compare favorably with the yields secured in the best sections of tha 

 Mississippi River Valley. The long growing season allows the planting of a 

 winter crop of oats, which is harvested early in the spring so as to allow the 

 planting of com en the same lands so that ii lias ample time ami favorable 

 Conditions for maturing in the autumn. The long and favorable growing sea- 

 son makes possible many combinations of crops. With some combinations the 

 same area of land produces three crops in a year. The mild winters make 

 stock raising profitable, as green teed can be grown during the entire year. 



NATURAL DRAINAGE CONDITIONS. 



The natural surface drainage of this section is away from the Mississippi 

 River and larger bayous of sedimentation, directly into the Gulf by way of 

 bayous of the tidal erosion type. However, numerous canals are being 

 cut through the bayous of the first type from the low-lying swamp or prairie 

 lauds, thus aiding in the drainage. Water covers the surface of the undrained 

 lands for the greater part of the year. This water comes from three different 

 sources — direct precipitation, river overflow, and tidal overflow. 



Overflow Due to Direct Precipitation. 



The water to be removed from these lands comes mostly from direct pre- 

 cipitation, and it is with reference to the removal of this water that the nature 

 and capacity of natural drainage channels will be discussed. 



Owing to the slight elevation of the land above sea level, all of the streams 

 are very sluggish in character. Their surface slopes ulways are very slight 

 and are due entirely to the piling up of the water in the interior until suffi- 

 cient head is created to force the water out to the Gulf. At times of high 

 tide in the Gulf and small precipitation in the interior, the current often is 

 reversed in many of the streams, and salt water then flows many miles inland. 

 However, at such times the water in the channels is so low that the tide rarely 

 causes a stage sufficient to flood any of the adjoining land. (This condition 

 should not be confused with tidal overflow, which will be discussed later.) 

 The fluctuation in water level, due to direct precipitation, in the various bayous 

 and interior lakes is never very great and depends quite as much upon the 

 drection of the prevailing winds as on the amount of precipitation. 



Bayou Lafourche is one of the largest and longest natural drainage chan- 

 nels in this section, extending about 120 miles into the interior. A gauge has 

 been maintained for more than seven years at a point about 70 miles inland from 

 the Gulf, and back about 1 mile from the bayou on a canal which connects 

 with the' general water level in the swamps. The extreme variation of the 

 water surface observed at this gauge was 4.5 feet. The lowest stage was 

 caused by a prolonged and record-breaking drought in the spring of 1010. at 

 which time salt water had reached the gauge. This reading, which is approx- 

 imately sea level, was 1.3 feet below the average stage of water at this point. 

 The highest stage was reached in October, 1916, after a rainfall of about 

 21 inches in 15 days, when the water stood 3.2 feet above average water level. 



At points farther inland the fluctuation in water level is proportionately 

 greater. The situation on Bayou Lafourche is mentioned because it is typical 

 of all the long, sluggish bayous that carry away the drainage water. Most of 

 the Interior watercourses are connected with each other by cross bayous and 

 canals, so that they are all somewhat similar in their action. The drainage 

 areas are very poorly defined and no doubt lap somewhat, as some of the con- 

 nect inif canals and bayous often reverse direction of current according to the 

 stages .of water in the various parts of the system ; for this reason it is prac- 



