River valley deposition: levee River valley deposition: levee formationformationRiver valley deposition: levee River valley deposition: levee formationformation

Gentle valley side

Gentle valley side

River flowing above height of floodplainRiver flowing above height of floodplain

Flat floodplain

Flat floodplain

Gentle valley side

Gentle valley side

Layers of silt deposited during

several floods

Layers of silt deposited during

several floods

Most silt deposited right beside river

channel

Most silt deposited right beside river

channel

Finest materials <<<<< Coarsest materials

Finest materials <<<<< Coarsest materials

Coarsest materials deposited right beside river channel where water speeds are fastest, but drop soon afterwards as flooding water moves from fast channel to broad floodplain. Lighter finer materials carried further even when water speed very low

Coarsest materials deposited right beside river channel where water speeds are fastest, but drop soon afterwards as flooding water moves from fast channel to broad floodplain. Lighter finer materials carried further even when water speed very low

A classic waterfall: headward A classic waterfall: headward erosionerosionA classic waterfall: headward A classic waterfall: headward erosionerosion

(5) Wearing back off soft rock exposes hard rock overhang which eventually breaks off under its own weight

(6) Water fall retreats upstream - headward erosion

(7) Steep narrow gorge develops

(3) Undercutting

(2) Soft Rock, e.g., sandstone or shale

(1) Hard Rock, e.g., gritstone or schist

(4) Deep plunge pool showing downward erosion through corrasion and hydraulic action. Usually full of debris from collapses above which is getting smaller, undergoing attrition

Neck gets narrowerNeck gets narrower

Meander core

Meander core

Ox-bow lake

Ox-bow lake

Meander loop bends

increasingly

Meander loop bends

increasingly

Fastest current on outside of bend

Fastest current on outside of bend

Meander neck

Meander neck

Slowest current on inside of bendSlowest current

on inside of bendSlip off slope

Slip off slope

River cliff

River cliff

River cuts through neck of land at time of flood

River cuts through neck of land at time of flood

The meander & ox-bow The meander & ox-bow lakelakeThe meander & ox-bow The meander & ox-bow lakelake

Fastest current and thalweg

Fastest current and thalweg

4

Point bar (slip off slope) created on

inner bank

Point bar (slip off slope) created on

inner bank

River cliff created on outer bank

River cliff created on outer bank

Lateral erosionLateral erosion

DepositionDeposition

Helicoidal flowHelicoidal flow

Hydraulic action, corrasion &

attrition

Hydraulic action, corrasion &

attrition

Concave profileConcave profile

Convex profileConvex profile

Faster current (Thalweg)

Faster current (Thalweg)

Slower currentSlower current

The meander: lateral The meander: lateral erosionerosionThe meander: lateral The meander: lateral erosionerosion

Centrifugal force

Centrifugal force