THIRD ANNUAL YEAR BOOK — PART I. 



25 



SURFACE DRAINAGE. 



STEEP SLOPES. — On ground with good natural underdrainage, as 

 on hillsides, surface ditches are sufficient to carry off surface water 

 from rain or snow. In order to prevent washouts on steep slopes, how- 

 ever, it sometimes becomes necessary to construct water breaks; that is, 



Fig. 3. — Poorly crowned and badly drained roadbed. 



broad, shallow ditches so arranged as to catch the surface water and 

 carry it each way into the side ditches. Unfortunately, some road build- 

 ers have an idea that the only way to prevent hills, long and short, from 

 washing, is to heap upon them a large number of those ditches known 

 in different sections of the country as "thank-you-ma'ams," "breaks," or 

 * "hummocks," and the number they sometimes squeeze in upon a single 

 hill is astonishing. Such ditches retard traffic to a certain extent, and 

 often result in overturning vehicles; consequently they should never be 

 used until all other means have failed to cause the water to flow into 

 the side channels. They should never be allowed to cross the entire 

 width of the road diagonally, but should be constructed in the shape of 

 the letter V, with the point uphill. This arrangement permits teams 

 following the middle of the road to cross them squarely and thus avoid 

 the danger of overturning. These ditches should not be deeper than is 

 absolutely necessary to throw the water off the surface, and the part in 

 the center should be the shallowest. 

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