TELEMATIC TEACHING PROJECT Fluvial processes and landforms glennkns

TELEMATIC TEACHING PROJECT Fluvial processes and landforms glenn@kns. wcape. school. za

FLUVIAL PROCESSES • Stream patterns • Stream piracy • Longitudinal and cross profiles • Rejuvenation

STREAM PATTERNS RADIAL • From highest central point (butte/conical hill) DENDRITIC • Tree • Uniform rocks TRELLIS • Alternating layers of hard and soft rock • Parallel streams RECTANGULAR • Bends 90° • Tributaries 90° • Joints and faults MUST KNOW THE FOLLOWING • What does it look like • Description • Underlying structures

DENDRITIC PATTERN Looks like the branches of a tree

TRELLIS PATTERN HARD SOFT

RECTANGULAR PATTERN

RADIAL PATTERN Radiates from highest central point like butte or conical hill

STREAM PIRACY A • Shortage of water • Farming disadvantaged • Problems - fishing • Recreation disadvantaged • Effect on Hydro electricity • Less water for Industries Misfit stream R A D W AT ER SH Headward erosion • Positive impact on farming • Positive impact on economy B • Flooding • Erosion • River deposits fertile soil • Increase in farming activities Wind gap Elbow of capture r ve B RS Ri r ive AT E HE ED Captor stream W

LONGITUDINAL PROFILE Drawn from source to mouth ‘n Rivier Rivers have ‘n anhet upper BOLOOP course ‘n a MIDDEL middle LOOP course and En a ‘n lower BENEDE LOOP course

CROSS PROFILE Drawn from one bank to the other LATERAL EROSION D O W N UPPER COURSE MIDDEL COURSE (MATURE) LATERAL EROSION LOWER COURSE (OLD)

CROSS PROFILE ROUND A BEND X Y Y X Deposition Slipoff Undercut Erosion Faste r flow Slower flow

UPPER COURSE (YOUNG RIVER) Downward erosion St ee p Spurs sl op es Narrow V-shaped valley

MIDDLE COURSE (MATURE) Gradual slope Meanders Lateral erosion Wide valley with floodplain

LOWER COURSE (OLD RIVER) MOUTH SANDBANKS SEA MEANDER WIDE CHANEL ALMOST FLAT FLOODPLAIN

ED ID A R B LOWER COURSE OF A RIVER R ST F L A T M EA D B A N K S H S R MA ME AN DE R S SA N M O U T H

UPPER COURS E MIDDEL COURSE LOWER COURSE S E A Almost flat Gradient Steep Gradual Speed Slow Very slow Lateral Erosion Deposition Meanders, Spurs Sandbanks, Marshes, Deltas, Oxbow lakes Fast Pro. Downward cesses Erosion Landforms Waterfall, Rapids,

What is happening here?

BASIS OF EROSION AND REJUVENATION Temporary base of erosion Middle course: Mature river flows slower Lower course: Old river flows very slow W HE R E? UPPER Permament base of erosion Young river flows fast REJUVENATION River starts flowing faster. Has renewed energy and Increased erosion HOW? • Sea level drops • Land rises • Increase in rainfall • Fast-flowing tributary

STRUCTURAL LANDSCAPES • Horizontal layers • Inclined layers • Massive igneous rocks

HORIZONTAL LAYERS

Large flat top Hard layer MESA

MESA

BUTTE AND CONICAL HILL

Smaller Larger Hard layer Teebus Koffiebus Conical hill (pointed butte) Butte

INCLINED LAYERS Scarp slope Dip slope N A T S I S RE K C O R T SO FT RO E CK R

P DI OP SL • Contours far • Gentle slope • Resistant layer • Dip slope E ES RP KA RP E A SK DIP SLO PE • Contours close • Steep slope • Softer layer • Eskarpment

MASSIVE Laccolith Dyke Pipe Sill Batolith Lopolith

TORS

TORS Tor after removal of weathered rock Joints Mechanical & chemical weathering

TORS

SLOPES AND MASS MOVEMENT

SLOPES Crest: Convex. Soil creep Free face: Steep. Deposition impossible Tallus: Straight & constant; deposition Pediment: Concave; deposition Knickpoint

TYPES OF MASS MOVEMENT Soil creep SLOW MOVEMENT Earth flows WATER VERY FAST MOVEMENT Land slides FAST MOVEMENT Rock falls

EVIDENCE OF MASS MOVEMENT Leaning poles d e k rac C n e k ro s d a ro s e c fen B g n i an Le Leaning trees tom s e n to s b

MANAGEMENT SOIL NAILS NETTING OTHER METHODS • Plant vegetation • Retaining walls • Drainage • Engineering techniques

THANK YOU for paying attention Thank you TONY HAMBLY who supplied some of the photos for this presentation