380 



REPORT OF OFFICE OF EXPERIMENT STATIONS. 



some land before them. In no case should the width of the berm be 

 less than that of the base of the dike, and when the embankment is 

 exposed to the action of the wind or waves it should be 100 feet or 

 more in mdth. The distance from the shore must be determined in 

 a great measure by the qualit}^ of the ground. It should be located 

 far enough away from the stream or shore to be secure against under- 

 mining b}^ caving. 



HEIGHT OF EMBANKMENT. 



After locating the dike the height is the next important element to 

 be considered. No one can tell with certainty to what point a storm 

 tide at any point will rise, but when observations extend over a long 

 term of years the greatest height reached may be safely taken as the 

 maximum that is likely to occur in the future. The height of the 

 embankment should be at least 18 inches above this mark. This 

 may seem excessive, but nothing less is absolutel}^ safe. When the 

 waves reach near to the top of the embankment and a strong wind 

 prevails, much damage is likel}^ to occur, and in case they overtop 

 the embankment the entire work may be greatly impaired or even 

 destroyed. 



CROSS SECTION OF EMBANKMENT. 



The form of dike best suited to turn water and its proper dimen- 

 sions are matters of the greatest importance. In nearly every case 



of failure the cause 

 has been found to 

 be that the em- 

 bankment was not 

 high enough and 

 was overtopped by 

 the waves, or the 

 cross section was 

 too light to with- 

 stand the pressure. 

 For the cross sec- 

 tion of the dike it 

 is not enough to 

 obtain ample 

 strength to resist 

 the force of the 

 water on the dike but this strength must be obtained at the lowest 

 possible cost. 



The form and area of the cross section of the embankment depend 

 largely upon the character of the material out of which the embank- 

 ment is made and the length of time the water will remain against 



BEfJM 



Form of Oikg made of doy or cljyey ham 



Form of D'kt mode of sand or sandy loom 



Form of Dike madt ofmucA soil 



Fig. 2.— Forms of dike made from different materials. 



