Erosion processes and control methods in North America

Wien

1978

S. 19-20

Unselbständiges Werk

200142891

Creep, slump-earthflows, debris avalanches and debris torrents are the major erosion processes operating on mountainous forest land and function as primary links in the natural transport of soil material to strems. In deeply weathered, clay-rich mantle materials, creep movement may range as high as 15mm per year. Where discrete failure occurs transport rates of material by slump-earthflow may increase by several orders of magnitude. On steep slopes characterized by shallow, coarse rained mantle materials and steep, incised drainages, debris avalanches and debris torrents transport large volumes of material to the stream at rates as high as 20m per second. Clearcutting and road construction accelerate these processes, the former by destroying the stabilizing influence of vegetation cover and altering the hydrologic regime of the site, the latter by exposing bare mineral soil and by interrupting the balanced strength-stress relationships existing under natural conditions by cut and fill activities, poor construction of fills and altering the hydrologic regime of the site, the latter by expositing bare mineral soil and by interrupting the balanced strength-stress relationships exising under natural conditions by cur and fill activities, poor construction of fills and alteration of surface and subsurface water movement.