5 RIVERS You need to know The four

5 RIVERS You need to know: • • • The four ways rivers erode The three stages of a river They features of the Youthful Stage The features of the Mature Stage The features of the Old Stage

4 Processes of River Erosion (1) Hydraulic Action – The force of the moving water wears away the banks and bed of the river. (2) Abrasion – Small stones carried by the river wear away at the banks and bed of the river

4 Processes of River Erosion (3) Attrition – The small stones in the river are worn down and broken up as they hit off each other. (4) Solution – Rocks and soil are dissolved by acids in the water.

THREE STAGES OF A RIVER (1) Youthful Stage (2) Mature Stage (3) Old Stage Steep so river flows very fast Fast water erodes easier Features are Waterfalls, V Shaped Valley Interlocking Spurs More gradual gradient so river slows down Features are Meanders Much slower river. As river slows down it drops the material it carries Called Deposition Features are Deltas,

FEATURES OF THE YOUTHFULL STAGE V SHAPED VALLEY WATERFALL INTERLOCKING SPUR

V SHAPED VALLEY RIVER FLOWS VERY FAST AND ERODES DOWNWARDS. EVENTUALLY FORMS A STEEP SIDED VALLEY.

INTERLOCKING SPURS AS THE RIVER FLOWS DOWNHILL IT MEETS AREAS OF HARD ROCK WHICH IT CANNOT ERODE SO IT FLOWS AROUND IT THE HILLY CURVES LEFT BEHIND ARE CALLED INTERLOCKING SPURS

WATERFALL AS A RIVER FLOWS OVER AN AREA OF HARD ROCK IT SPEEDS UP AND WHEN IT HITS THE AREA OF SOFT ROCK BEYOND IT ERODES IT QUICKER. EVENTUALLY IT WEARS THE ROCK AWAY FORMING A DROP OVER WHICH THE RIVER FALLS.

FEATURES OF THE MATURE STAGE MEANDER

MEANDER • A river flows faster on the outside of a bend so it erodes here • The water is slower on the inside so it deposits here. • Over time the erosion one side and deposition on the other increases the curve of the river forming a meander

FEATURES OF THE OLD STAGE WHEN A RIVER REACHES THE OLD STAGE IT SLOWS DOWN AND CANNOT CARRY ITS LOAD. IT STARTS TO DUMP ALL THE SAND, ROCKS AND MUD IT CARRIES. THIS PRODUCES TWO KEY FEATURES: • DELTAS • LEVEES

DELTA • WHEN A RIVER REACHES THE SEA IT DROPS ALL ITS MATERIAL WHERE THE RIVER MEETS THE SEA, CALLED THE MOUTH. • IT FORMS LITTLE ISLANDS IN THE MOUTH OF THE RIVER. • WE CALL THIS A DELTA.

LEVEE • WHEN A RIVER FLOODS IT DROPS ITS LOAD AT THE EDGE OF THE FLOOD. • OVERTIME THESE FLOOD MATERIAL BUILDS UP TO FORM BANKS ON EITHER SIDE OF THE RIVER CALLED LEVEES

Erosion or Deposition V shaped Valley Meander Fast flowing river Waterfall Delta Slow flowing river Levees Youthful, Mature or Old Stages of a River

KEY TERMS YOU NEED TO KNOW • • • • HYDRAULIC ACTION ATTRITION ABRASION SOLUTION YOUTHFUL STAGE WATERFALL V-SHAPED VALLEY INTERLOCKING SPUR MATURE STAGE MEANDER OLD STAGE DELTA LEVEE