Lornshill Academy. Geography Department National Revision Physical Environments Rivers

Transcription

1 Lrnshill Academy Gegraphy Department Natinal Revisin Physical Envirnments Rivers

2 Revisin Ntes fr Rivers What yu need t knw: 1. Hw rivers erde, transprt and depsit. 2. The Upper Curse: Frmatin f a V-shaped valley and a Waterfall 3. The Middle Curse: Frmatin f a Meander 4. The Lwer Curse: Frmatin f an Ox Bw Lake, Fld Plain & Levees 5. River map wrk 6. Hw peple use river landscapes Rivers are ne part f the glbal water cycle returning water frm the muntains t the sea. The area arund the river is called the Drainage basin. It is given this name because any rain which falls within this area drains int that river. 1. Ersin, Transprtatin & Depsitin Prcesses f River Ersin: Hydraulic Actin: The sheer frce f the water hitting the river banks and flwing ver the river bed and wearing dwn the rck. Crrasin: The banks are erded by the rcks the river carries. These act like sandpaper, scraping and smthing the banks as they mve past. The river bed is erded by the larger rcks buncing alng and hitting the rck underneath until it breaks. Attritin: This is where the rivers lad hits and rubs against each ther, and als the river bed and banks. This makes the particles smaller and mre runded.

3 Prcesses f Transprtatin: Tractin: Rlling stnes alng the river bed. This requires lts f energy. Suspensin: Clay sized particles are carried alng by the river flw. Saltatin: Sand sized particles bunce alng the river bed. Slutin: Sme minerals are disslved by the river water. Depsitin ccurs when the river lses energy and/r the river has t much lad. One way f thinking abut rivers is t divide their jurney up int three sectins: Upper Curse Middle Curse Lwer Curse Curse Main Activity Main Features Surce, tributaries, V- Upper Curse (steep gradient) Middle Curse (gentle gradient) Lwer Curse (very lw gradient) Vertical (dwnward ersin) Lateral (sideways) ersin starts, transprtatin Depsitin shaped valley, interlcking spurs, waterfalls, grges, rapids. Meanders, River Beaches, River Cliffs. Fldplains, Ox Bw lakes, levees, estuary 2. Landfrms ften fund in a River s Upper Curse: a) V-shaped Valleys:

4 Rivers begin high up in the muntains s they flw quickly dwnhill erding the landscape vertically. The river cuts a deep ntch dwn int the landscape using hydraulic actin and crrsin. As the river erdes dwnwards, sme f the rcks fall int the river and this helps the prcess f crrsin, leading t further ersin. The river transprts the rcks dwnstream and the channel becmes wider and deeper creating a V-shaped valley between interlcking spurs. b) Waterfalls: The river flws ver bands f sfter and harder rcks. Sfter rck is mre quickly erded. The river undercuts the harder rck leaving an verhang. The river frms a plunge belw the waterfall. Overhanging rck is unsupprted and falls int the plunge pl. The waterfall mves upstream. This prcess cntinues and a grge is cut back int the hillside.

5 3. River Landfrms ften fund in the Middle Curse: Meanders: The bends in a river are called meanders. Once frmed they get mre and mre bendy because the water is frced t g faster arund the utside bend. This causes ersin and makes the river deeper here. The riverbed at the utside bend gets undercut and a river cliff frms. On the inside bend, the river is flwing mre slwly. This causes it t depsit (r drp) sme f the material it was carrying. This makes it shallwer n the inside bend frming what is called a river beach (r slip-ff slpe). 4. River Landfrms ften fund in the Lwer Curse:

6 a) Ox-bw Lakes: These frm when a meander gets very bendy (diagram 1). As this cntinues the neck between meanders gets narrwer and narrwer (diagram 2). Eventually during a fld the river cuts acrss the meander neck (diagram 3) erding a new channel. Over time the ld meander lp becmes detached frm the river by the river depsiting material (diagram 4). This is called an x-bw lake and it will eventually dry up and disappear. b) Fld Plains: When a river flds it leaves behind fine silt (called alluvium). This can flatten and smth ut any small bumps in the landscape. The flat land next t a river is called a fld plain. It is shwn n an OS map by white space (i.e. n cntur lines) next t a river. c) Leveés:

7 As sn as the river verflws the river channel and bursts its banks, the water ges frm being in the deep river channel t suddenly spreading ut ver the fld plain. This causes an increase in frictin that can result in bigger stnes being depsited here. These can build up int natural embankments either side f the river channel called levees. On an OS map they are shwn by small black triangles next t the river. The river is n its fldplain with a very lw gradient. The river is mainly depsiting (silt and sand). When the river flds a lt f silt is depsited n the river banks and much less n the fldplain. Frequent flding cntinues this build up. When the river is flwing nrmally it depsits in the river bed. This raises the river abve the fldplain. Usually the built-up levées prtect the plain frm flding.

8 5. River Map Wrk V-shaped valleys: On an OS map, V- shaped valleys are shwn by the cntur lines bending in a V arund the river: Waterfalls: Where there is a waterfall n an OS map, the wrd waterfall will be written in blue writing.

9 6. Hw d peple use River Landscapes? Over the curse f a river, frm muntains t the sea, there are many ways that peple use the land. Fr example: Farming In the Upper Curse there are ften hill-sheep farms and as we get nearer t the lwer curse the type f farming change t being mre arable. On the fld plains f the river in the lwer curse, the type f farming is ften pastral keeping animals like cws r pigs. These like the grass that grws well n a river fld plain, and they can be easily mved t safety if the river flds.

10 Frestry On the steeper slpes f the Upper Curse f rivers, frestry is a gd way f using the land. Trees grw well n the steeper slpes and this is a way f using land that is difficult t use fr anything else. Hydrelectric Pwer and Reservirs Rivers can prvide clean and renewable energy in the frm f hydrelectric pwer in the upper curse. Dams can als be built t create reservirs, which supply ur twns and cities with water. Recreatin and Turism Rivers are used fr varius recreatinal pursuits: Upper Curse- white-water rafting, grge walking, sightseeing eg waterfalls. Middle and Lwer Curses- Gentler slpes and gd access via rads and railways t bth lwer and upper curse features means lts f turists stay here in B&Bs (ften prvided by farmers) and caravan and campsites.