272 MISCELLANEOUS FARM SUBJECTS 



well, more forcibly illustrated than in the building of dikes and 

 levees. The design and construction of the levees, ditches, and 

 pumping plant require a considerable degree of engineering ability. 

 Poor design may result either in a system so inadequate for its pur- 

 pose as to yield a benefit to the land insufficient to make the under- 

 taking profitable, or it may lead to an expenditure for construction 

 greatly in excess of the amount that could have been made to suffice. 

 In general, the inexperienced tend to underestimate greatly the ex- 

 tent and expense of the work required in such reclamation. 



The levees must originally be made of such height and thick- 

 ness as to afford ample strength and they must also be given careful 

 subsequent attention to secure proper maintenance. The internal 

 drainage ditches should be deep enough to keep the ground water 

 level at least 3 feet below the surface and their capacity should be 

 sufficient to discharge heavy rains freely to the pumping station. 

 Streams entering the district from higher ground should be diverted 

 around the levees where such a plan is feasible. 



The pumping plant should have a capacity sufficient to remove 

 as a minimum amount in 24 hours a quantity of water sufficient to 

 cover the entire district to a depth of one-fourth inch. The capacity 

 should be greater in situations of heavy rainfall and where the run- 

 off of rolling land is received in the district. The pumping ma- 

 chinery should be so arranged as to reduce to a minimum the work 

 of disposing of the surplus water, and it should be chosen with 

 especial regard to economy and efficiency. 



The strip of land occupied by the levee should not be located 

 too close to the natural banks of the stream whose waters are to be 

 diked off. Consideration must be given to the question of leaving 

 outside the levee a sufficiently wide flood channel. The conclusion 

 reached in any particular case will depend upon the conditions ex- 

 isting upon the opposite banks of the stream, and no definite rules 

 can be stated. If the banks of the stream are subject to cutting or 

 caving, the question of the future permanence of the levee enters. 

 A strip of timber should be left outside the borrow pit to form a pro- 

 tection to the levee during high water against erosion by too strong 

 a current, and against destructive wave action during high winds. 

 Where practicable, bars across the borrow pit should be left at in- 

 tervals so as to prevent top strong a current near the levee. No sharp 

 corners should be made in the line of the levee's location. 



System of Ditches. In planning a system of ditches it should 

 be the aim to locate them in such a way as to leave the land in the 

 best possible shape for cultivation. Where there is high land that 

 drains into the marsh, an intercepting ditch should be cut along the 

 foot of the slope to lead the water into the storage basin without 

 overflowing the low land. The depth of the ditches required and 

 their distance apart depend largely upon the character of the soil. 

 The main ditch should be as deep as the sill of the tide gate, while 

 the laterals should range from 2 1 /2 feet deep at the upper end to 3 

 or 3 l /2 feet at the lower end, according to the depth of the outlet 

 channel. In most places ditches in marsh soil will stand with almost 



