Gradient and Channel in Characteristics
The slope of a stream channel expressed as the vertical drop of a stream over a specified distance is gradient. Portions of the lower Mississippi River have very low gradients of 10 centimeters per kilometer or less By contrast, some mountain stream channels decrease in elevation at a rate of more than 40 metersper kilometer- gradient 400 times steeper than the lower Mississippi (Figure5.7) Gradient varies not only among different stream but also over a particular stream's length. The steeper the gradient, the more energy available for streamflow. If two streams were identical in every respect except gradient, the stream with the higher gradient would obviously have the greater velocity.
A stream's channel is a conduit that guides the ilow of water, but the water encounters friction as it flows. The shape, size, and roughness of the channel affect the amount of friction. Larger channels have more efficient flow because a smaller proportion of water is in contact with the channel. A smooth channel pro motes a more uniforma flow, whereas anirregular channel filled with boulders creates enough turbulence to slow the stream
Gradient and Channel in Characteristics The slope of a stream channel expressed as the vertical drop of a stream over a specified distance is gradient. Portions of the lower Mississippi River have very low gradients of 10 centimeters per kilometer or less By contrast, some mountain stream channels decrease in elevation at a rate of more than 40 metersper kilometer- gradient 400 times steeper than the lower Mississippi (Figure5.7) Gradient varies not only among different stream but also over a particular stream's length. The steeper the gradient, the more energy available for streamflow. If two streams were identical in every respect except gradient, the stream with the higher gradient would obviously have the greater velocity. A stream's channel is a conduit that guides the ilow of water, but the water encounters friction as it flows. The shape, size, and roughness of the channel affect the amount of friction. Larger channels have more efficient flow because a smaller proportion of water is in contact with the channel. A smooth channel pro motes a more uniforma flow, whereas anirregular channel filled with boulders creates enough turbulence to slow the stream
การแปล กรุณารอสักครู่..
