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