erosion in rivers
abrasion - this process involves the river beds and banks being worn down by the rivers load at high velocity
hydraulic action - this is the process of the river beds and banks being worn down by the force of the river water
attrition - this is the process where the river picks up material and the material bangs into each other, breaking down and smoothing
corrosion - this is a chemical action of the acid in the river water slowely dissolving the bed and the banks
when the river going from the higher parts of the river to the middle part it has surplus energy to get rid of this the river begins to meander.
the outside bend is the fastest part of the river and this causes erosian and the formation of a river cliff. (shaped much like a small cliff, and are formed by the erosion of soil as the stream collides with the river bank) .the inside bend is the slowest part and at this part the river deposits its load and the formation of point ban ( an area of depostion) this is the shallowest part of the river.
the thalwig is the fastest flowing part of the river.
ox bow lakes
After a meander has been created the erosion of the outside and the deposition on the inside will carry on and the neck of the meander gets narrower, untill the meander is almost complete circle.
at this point the river may cut across the narrow neck. this straightens the channel and gives a more direct course for the river. the abandoned meander, left isolated on the flood plain is know as an ox bow lake.
hard and soft engineering
methods of preventing floods from causing mass distruction
soft engineering - this is a method of preperation rather than constructing things. this is better for the environment.
- flood plain zoning
- texting people when a heavy rain is
- plant trees in dranage basin
hard engineering - it the method of building large constuctions to prevent floods
- resevaurs and dams
- raise levees and staighten rivers
causes of flooding
natural causes -
- long periods of heavy rain
- snow and ice melting very quickly
- a cloudburst in a thunderstorm causes a large amount of rain to fall
- building towns and increasing urban areas makes surface impermiable so more surface/water run off
- deforestation reduces interception and increases surface run off