11: Stream Processes, Landscapes, Mass Wastage, and Flood Hazards

oxbow lake

a curved lake that is created when a stream cuts off a meander

stream terraces

a flat benchlike structure produced by a stream which was left elevated as the stream cut downward

deranged pattern

a random pattern of stream channels

annular pattern

a set of incomplete concentric rings of streams connected by short radial channels develops on eroding domes and folds that contain alternating folded layers

braided channels

a stream that consists of numerous intertwining channels

head

a stream's point of origin

delta

an accumulation of sediment formed where a stream enters a lake or an ocean

radial pattern

channel flow outward from a central area water drains from the inside of the pattern to the outside of the pattern develops on conical hills like volcanoes or domes

centripetal pattern

channels converge on a central point, often a lake or playa, center of a closed basin water cannot drain

point bar

crescent-shaped accumulation of sand and gravel deposited on the inside of a meander

levees

deposit of sediment at the edge of a river higher than the rest of the floodplain

floodplains

develop when alluvium accumulates landward of the river banks during floods

alluvial fan

fan-shaped deposit of sediment formed when a stream's slope is abruptly reduced occurs where a steep-gradient stream abruptly enters a wide, dry, plain

shape of river valley varies because of these factors

geology gradient base level discharge load

meandering

highly sinuous

sinuosity

measure of how much a stream meanders side to side length/straight line distance from start to end

sheet flow

moves downslope in response to the pull of gravity

rectangular pattern

network of channels with right-angle bends that form a pattern of interconnected rectangles and squares usually develops over rocks that are fractured or faulted

deposition

occurs if the velocity of the stream drops or if parts of the stream evaporate

weathering

occurs where the stream physically erodes or disintegrates Earth materials and where it chemically decomposes to form. sediments

cutbanks

outer edge of the meanders area of active erosion

trellis pattern

resembles a vine where the main stream is long and intersected at nearly right angles by its tributaries develops where alternating layers of resistant and nonresistant rocks have been tilted and eroded to form parallel ridges and valleys

dendritic pattern

resembles the branching of a tree water flow: from branch-like tributaries to the trunk-like mainstream or river also develops where a stream cuts into homogenous rock

escarpments

steep slopes or cliffs separating the horizontal stream terraces

gradient

steepness of the slope along a selected length vertical rise or fall/horizontal distance (m/km)

headward erosion

stream channels deepen and erode their V-shaped channels uphill through time

load

the amount of material that is transported by a stream

stream drainage pattern

the arrangement of stream channels and tributaries that forms on a landscape as a result of its underlying geology and relief

geology

the bedrock geology over which the stream flows

mass wastage

the downslope movement of Earth materials

mouth

the end of the river valley where it enters an outlet waterbody or a dry basin water dispersed into larger area velocity decreases sediment settles to form an alluvial deposit

drainage basin

the entire area of land that is drained by one stream or an entire stream drainage system

divides

the linear boundaries that separate one drainage basin from another difficult to identify in areas of lower relief

base level

the lowest level to which a stream can theoretically erode

discharge

the rate of stream flow at a given time and location

uplands

the smallest valleys in a drainage basin occur at its highest elevations erosion is dominant process

normal stage

the water level of a river is below the river's banks

channel bars

underwater sandbars

stream drainage system

water is channelized, it falls into small stream channels that eventually merge to form larger streams. Larger streams merge to form rivers, and rivers flow into and outlet waterbody

bankfull stage

water level is even with the banks

transportation

weathered rocks are dragged, bounced, and carried downstream

three main processes in every stream

weathering transportation deposition

flood stage

when the water level exceeds the banks