When stream slows, sediment is deposited.

Examples:
deltas form where streams flow into lakes or ocean
alluvial fans: where streams flow from mountains into valleys

Types of streams:

Braided: many channels that split and rejoin
Meandering : channel curves and bends
        Meandering streams migrate by erosion at outside of curves and deposition at inside of curves.
        Incised meanders: meandering stream cuts downward to form deep valley
 
 

Floods: occur when the discharge is greater than the channel can carry.
During floods:

• Ridges of sand (natural levees) deposited at edge of channel.
• Silt and clay deposited on floodplain.

• Paved surfaces
• Urbanization increases flood peak on hydrograph (discharge through time)
• channel constriction
• Filling of wetlands: removes water storage area
• Removal of vegetation: increases runoff of water and sediment

Flood prediction:

short-term
    stream monitoring
    Flood predictions: based on stream levels, precipitation, and past behavior

 long-term:  Identify flood recurrence intervals, “100-year flood”: 1% chance during a particular year.
 

Flood Reduction:

Solutions: sediment “dams”, retention ponds, wetlands restoration

Damage Prevention engineering (levees, dams)

levees: build up sides of channel
But levees can fail, and can increase downstream flooding.

Dams: store floodwater and release it slowly.
Also used for: recreation, power, irrigation water

• land inundated behind the dam.
• disturbance of plant and animal life
• Sedimentation limits life of dam