Earth-transport sediment to the oceanFactors in StreamflowStream Channels* the passageway is called a channel* the load is the sediment and dissolved matter the stream transports (kg/m3)* the discharge is the volume of water passing a given point at a given time (m3/s)* gradient- the vertical distance a stream cannel falls between two points (m/km)* long profile- long curve of gradient from stream's mouth to delta (m2)Dynamics of Streamflow* runoff- the portion of precipitation that flows on land surface* overland flow- broad sheets of runoff moving down slope* streamflow- the runoff and overland flow that flows in defined channelsChanges Downstream* discharge increases* channel cross-sectional area increases* velocity increases slightly* gradient decreases* grain size decreases* mineralogy may changeFloods (when the stream's discharge exceeds the capacity of the channel)* First, discharge increases (shown by hydrograph)-channel is scoured-cross-sectional area increases-velocity increases* Then, discharge decreases-sediment is deposited-cross-sectional area decreases-velocity decreases* Floods are predicted using frequency curves.* Catastrophic floods are rare (Columbia River)Base Level (level below which a stream cannot erode the land)* types of base levels:-sea level (base level for most streams)-lakes-natural dams (landslides & lava)-artificial damsChannel Patternsfactors* stream gradient* discharge* sediment loadTypes of Channel Patterns* straight channels- rare, sinuous max. depth, sandbar on opposite side* meandering channels- "switchback" bends in stream, gentle gradients-max velocity @ outer curve, pointbars on inner curve-oxbow lakes result from two meanders intersecting* braided stream- water divides and reunites through interconnected channels-separated by bars or islands-occurs most in streams w/ highly variable discharge and erodible banks-only 10% active at a given timeErosion by Running Waterbefore streams form* sheet er...
