14 Surface Water and Floods

Drainage basin

the total area drained by a stream and its tributaries

Divide

ridge or high ground that divides one drainage basin from another

Continental Divide

separates the streams that flow into the Pacific from those that flow into the Atlantic and Gulf of Mexico

Dendritic

drainage pattern resembling the branches of a tree

Radial pattern

streams diverge outward like the spokes of a wheel, such as on conical mountains

Rectangular pattern

tributaries have frequent right-angle bends

Trellis pattern

streams forming alongside parallel ridges & valleys

Discharge

volume of water passing a particular point in a stream over time

cutbank

zone of erosion (more erosion than deposits)

Point bar

dominent deposition (low velocity, more deposits than erosion)

Channel Shape

Shape of stream bed

Roughness

bedrock material (changeable)

Juvenile (young) river

High velocity, steep, U shaped sides, can erode any sediment, can cary large sediments, tend to cut/erode vertically more than laterally, can form braids.

Braided Streams

High velocity river carrying enough sediment to randomly deposit mounds of sediment. Can form through storm surges

Waterfall formation step 1

falling water and rock particles or boulders loosen and wear away the softer rock

Waterfall formation step 2

the hard rock above is undercut as erosion of the soft rock continues

Waterfall formation step 3

the hard rock collapses into the plunge pool to be broken up and washed away by the river. The position of the falls moves back.

Waterfall formation step 4

erosion continues, and the waterfall slowly eats its way, upstream, leaving a gorge behind

Mature (middle aged) rivers

Moderate gradient, can erode some sediments, wider than juvenile, erosion roughly equals deposition, flood plain beginning.

Old age rivers

Slow moving, shallow gradient, only erodes small/dissolved sediments, wide floodplains, wider than deep, deposition is higher than erosion.

Levees

mounds of sediment deposited from flooding. (looks like a berm).

Oxbow (or horseshoe) lake

Used to be a tight bend in river, but eroded away.

River timeline

Delta

body of sediment deposited at the mouth of a river when flow velocity decreases

Grand canyon formation process

Tectonic uplift of the Colorado Plateau caused the river to act young again and carve the canyon

Two factors of flooding

clay rich soils, water table close to the surface

Urban flooding

Hardtop surfaces inhibit infiltration and increase rapid runoff

Artificial levees

designed to increase capacity of river channel and works well until stream overtops levees, leading to extremely rapid flooding and erosion

Flooding solutions

Dams, Artificial levees, wise land-use planning

Delta

Old age river system, carries small particles

Alluvial Fan

Juvenile river system, carries large particles