Rivers
Flood plain deposits
-streams overflow their banks, carrying mud and sand that spreads across the floodplain -flood water away from the channel loses velocity and deposits sediment on the floodplain and forms a natural levee
Two types of streams
Braided: steeper gradient and/or heavy, coarse sediment load Meandering: gentle gradient and sediment load is finer
Channel Width and Depth Importance
Channel shape (if you were to take a slice) affects velocity because even those the cross sectional area is the same the perimeter in contact with water changes → less water touching perimeter, faster it will go
How is sediment deposited?
Deposition occurs discharge, velocity, and slope decrease
How do streams and rivers get their flow?
Direct, flow from upstream, surface runoff, groundwater
What is velocity? The equation? What are factors that affect velocity?
Distance water travels in a given time (V=D/T) Channel Shape, Roughness, Discharge (water quantity)
What is the term for the large areas that determine where a raindrop will go?
Drainage Basin
Where does the water go from rivers?
Evaporation, flow downstream, groundwater
Cross Section of the Lower Course
Gentle slope • Deposition dominates • Load is fine material • Flood plain, levees, point bars, cut banks, oxbows • Wide, deep channel
Cross Section of the Middle Course
Moderate slope, lateral erosion and deposition, load is becoming small and rounded; flood plains, meanders; pool-riffle sequences
How does sediment move?
Most transport done during flooding, and most sediments deposited when flooding stops
What separates Drainage Basins? What is that called? What is the name of the largest one in North America?
Ridges, Drainage Divides, Continental Divide
Sinuosity
Sinuosity is a measure of how winding the course of the stream is Sinuosity = channel length/straight distance (curvy have high sinuosity) - related to gradient; high gradient streams are less sinuous
Cross Section of the Upper Course
Steep slope, vertical erosion, load is large and angular, waterfalls and rapids are common
River Mouths
Topography flattens water loses speed deposition of sediments • Fan deposits, mouth bars, deltas
What is a watershed?
a drainage basin, or the area from which a stream gathers water; when rivers join together to form networks
What are point bars?
deposition that forms on the inner side of a river on a curve due to lower velocities and increased friction
Are sinuosity and gradient directly or inversely proportional?
inversely
What are flood plains?
low-lying, flat areas adjacent to channels
Is the velocity the highest in the middle of the stream?
not always; depends on its shape (if curved, centripetal force pushes water to the outside, making that area the highest velocity)
Where is velocity the slowest?
on the sides and bottom where flow is impeded by turbulence and friction
What are cut banks?
outside of a water channel undergoing erosion
Why do rivers become more "S" shaped over time?
outside of the river erodes and deposition occurs, eventually forms oxbow lakes
Stream terraces
remnants of floodplains of earlier streams when a stream with an existing floodplain down cuts and erodes laterally, a new lower floodplain forms and remnants of the older, abandoned floodplain remains along the valley margins
What is gradient? How does the gradient change depending on where it is in the river?
rise over run As a river travels downstream, the slope decreases (steep near origin, gentle downstream)
Discharge: definition and equation
the volume of water passing a particular point in a given period of time Q (discharge) = V (velocity) x A (cross sectional area: height x width)
Does changing land affect running water?
yes; urban development produces more stream discharge
What are pools and riffles? Why are they important?
Pools have slow, deep water Riffles have shallow, fast water Both are important for: - Hydrological processes - Water chemistry - Ecosystem health
Multiple Stream terraces
The process may be repeated many times in the course of a stream's history, so streams many be bordered by several terraces at different elevations above the active stream. • Highest terraces were the first to form = OLDEST