Environmental Engineering Reference
In-Depth Information
FIGURE 7.21
Rock Creek. District of Columbia — an example of a young stream eroding rock. (
From USGS quadrangle sheet.
District of Columbia; scule 1:24,000
.) (Courtesy of USGS.)
of major rivers where seasonal high runoff carries large quantities of coarse materials
downslope until a flat portion or low gradient is encountered. The coarse sediments are
dropped and then continue to move downstream as a result of periodically increased flow.
Deposits are typically sand and gravel mixtures in the channel. A moderately crooked
channel flowing through formations of hard granite and gneiss is shown in Figure 7.22.
FIGURE 7.22
Moderately crooked stream channel flowing through hard granite and gneiss; direction fault controlled. Extent
of flood plain apparent as tree line (Rio Itapicuru, Bahia, Brazil).
