LEVEES. 93 



seepage, and a little later by its entire stoppage, followed by no further inclination of 

 the mass to move, but rather by a commencing to dry out. Of course this treatment 

 does not apply to crayfish or other leaks where there is a channel of any considerable 

 size. If sloughs be treated when they first occur, or, better still, before they occur, 

 when their approaching occurrence is clearly indicated to the experienced eye by the 

 accumulation of moisture on the land slope, much annoyance and expense can be avoided." 



(4) Wave wash has been mentioned as one of the causes of levee failure. It attacks 

 the river face of levees, particularly new ones, owing to the wind or the passage of boats. 

 When trees intervene between the levee and the river its effect is not felt, or if it is, 

 it is not usually disastrous. 



Where winds continue with considerable strength for several days, as is often the 

 case during the spring, it is no easy task to maintain the levees. The waves roll at 

 considerable heights and strike with force, and it requires good material to withstand 

 their action. The following methods have been tried for the prevention of wave wash: 

 i. Placing a continuous strip of bagging or burlaps along the zone of the levee slope 

 affected by the waves and securing it by pegging it to the ground; 2. placing sheets 

 of corrugated iron, overlapping longitudinally; 3. building a bulkhead of boards along 

 the front slope; 4. securing a floating boom, composed of logs chained together, along 

 the levee. 



The most general method used, however, is to protect the part of the slope affected 

 with bags filled with earth, placed something after the manner of shingling a roof. 

 Each of these methods is very expensive and has its objectionable features, and where 

 the extent of the damage is not likely to prove a menace to the actual safety of the 

 levee it would probably be better to make no expenditures for protection against wave 

 wash, as it might be cheaper to replace the material washed away after the water has 

 subsided. 



The work of restoring the slope and resodding should be done as soon after the flood 

 as practicable, in order to allow the new material all the time possible to settle and the 

 new sod to have all the advantage of the early season to get well set and obtain a good 

 growth before another flood. Much good could be done by cultivating a growth of 

 willows and cottonwood along such exposed fronts to break the force of the waves. 

 Both of these plants are very hardy and have a rapid growth, and it is probable that 

 plowing a few furrows and covering up live portions of willows and cottonwood would 

 be sufficient to build up a living breakwater which would be very effective and inex- 

 pensive in future levee protection. 



(5) Cutting is the fifth and last cause given for the failure of levees. This is rare, 

 although through maliciousness, deranged mind, or other reasons levees have some- 

 times been cut. It is virtually impossible to guard against it unless the systems are 

 placed under strict police surveillance, and this is not practicable. 



Regarding levee failure an authority states that: "In spite of all precautions a 

 crevasse will sometimes occur. It is generally because of some hidden defect which 



