Floods

Environmental Impacts of Flooding

Flood: sea level rise + rivers/streams exceeding their capacity

Streams: erode the land, transport eroded particles, and deposit them based on velocity (energy)

• as velocity increases, erosion increases

• as velocity decreases, deposition increases

Flood Plain: flat area of water that fills up with water during a flood

• velocity decreases once stream overflows into the floodplain

• large amount of deposition

Sediment Transport: how variable velocity carries sediment

1. Dissolved Load: ions dissolved and carried in the water (easies to transport)

2. Suspended Load: fine particles carries above the stream bed

3. Bed Load: particles carried along the stream bed (largest, hardest to transport)

Variable Velocity: creates unique stream features due to erosion and deposition

• meandering channels: have higher velocity on curves

• straight rivers: have higher velocity in the center

• increased erosion on the outside: cut bank

• increases deposition in the inside: point bar (built material)

• oxbow lake: lake from the cut off section of a river

• braided stream: multiple small channels that consolidate into one, have larger sediment load

Stream Channel Shape: dependent on the landscape

1. the lower the gradient, the more the meander

2. V shaped = located upstream with the most velocity and most elevation

3. Meander = located downstream with the least velocity and flattest surface

Flooding: unusually high streamflow discharge due to rapid rainfall, extended rainfall, or snowmelt

1. dry flood plains become inundated

   • this is a natural, repeated process that happens over centuries that forms fertile land

2. Flood Frequency Curve: prediction of flood magnitude and recurrence interval (used by flood insurance)

   1. Recurrence interval = 1/(probability of flood occurring in any year)