r&b: a river's response

what three factors will slowly change a channel's morphology?

geology, gradient, and valley formation

what four factors will quickly change a channel's morphology?

hydrology, sediment input, flow obstruction, and riverside vegetation

what is catchment vegetation?

vegetation that catches a lot of water during rainfall; affects runoff

what two factors are external controls of channel morphology?

climate and catchment vegetation

lane's balance

according to lane's balance, if water discharge and/or slope increase, what happens to the channel?

erosion

according to lane's balance, if sediment discharge and/or grain size increase, what happens to the channel?

aggradation

what are the two types of terraces?

fill and strath

fill terraces

indicative of large-scale aggradation that buries valley; occur in alluvium channels only

strath terraces

indicative of large-scale erosion (with some aggradation); requires rock uplift to occur (changes base level)

how do dams affect rivers? (3 ways)

trap sediment and water both; decreases both sedimentation and discharge downstream; leads to biotic impacts

how does modern ranching and farming affect rivers? (4 ways)

degrading and eroding of banks; weight of animals can cause failure in fine-grained floodplains; larger slump erosion in wetland streams; fine sediment enters and new geometry of river forms

how does logging affect rivers?

more erosion due to less soil cohesion and more runoff; lack of large woody debris (LWD) equals loss of anastomosing channels