PROBLEMS AND RESULTS IN ISRAEL 407 
Figure 3. Dense plant cover obtained by efficient water spreading. 
Terrace thickly covered by Avena sterilis; slopes carry Zygophylletum 
dumosit. Uncovered patches on terraces received insufficient water 
(drought year!). 
of the wadi. At the side of the field adjoining the wadi bed a stone 
wall protects the plot from erosion by the flood water. The terraces 
thus formed are very broad, completely level, and one only slightly 
lower than the next. Onto these terraces water is diverted and 
spread by channels running obliquely from the watercourse. 
However, the force of the water often demolishes these channels. 
The ancient civilizations overcame this difficulty by constructing 
a solid low stone dam, a few meters thick, at a point below the 
opening of the channel. The height of this dam controlled the 
height of the flood water at the mouth of the channel, all excess 
water flowing over thedam. The force and amountof water entering 
the channel were controlled by the shape and size of its opening. 
We have developed a type of detention dam at a point above 
the channel calculated to catch most of the flow. The dam is 
pierced by a large diameter pipe, which permits the flow of a 
