Fluvial process

Fluvial process

1. FLUVIAL PROCESSES

2. Introduction Fluvial Processes Stages Of River Young Stage Classification of valley Maturity Stage Meanders Old Stage Alluvial Fan Rejuvenation Drainage Pattern Conclusion CONTENTS

3. “ As the different erosional agents act upon the earth’s surface there is produced an orderly sequence of land forms” orderly sequence of erosional features are formed at different stages in fluvial processes. INTRODUCTION

4. Fluvial processes: The set of mechanisms that operate as a result of water flow within a stream channel, bringing about the erosion, transfer, and deposition of sediment. Fluvial process is Exogenetic processes which includes River Erosion River Transportation River Deposition FLUVIAL PROCESSES

5. Erosion processes include the displacement of bed particles through drag and lift forces; abrasion, causing the wearing away of bed and banks as mobile agencies obtain and remove rock debris Transportation: processes include the transfer of material in solution and suspension, and by saltation. Deposition: is the geological process by which sediments, soil, and rocks is added to a landform or land mass. Contd..,

6. Young stage Maturity stage Old stage STAGES OF RIVER

7. It has steep sided and narrow v-shaped valley created by vertical erosion Characterized by waterfalls and rapids Water is often quit clear because the river is not carrying much load in suspension Stream meandering may exist in youth but the meanders in valleys incised below the upland surface Waterfalls or rapids may exist where stream courses cross beds of particularly resistant rock YOUNG STAGE

8. Upper zone: large, Angular boulders often block river channels Produces a large wetted perimeter leads to high friction which uses up much rivers energy After friction overcome there is little energy is available for eroding and transporting material, and forms steep slope. EROSIONAL LANDFORMS: V-SHAPED VALLEY

9. Genetic classification: Consequent valley: it is one whose course was supposedly determined by the initial slope of the land newly created Subsequent valley: these are valleys whose course have been shifted from the original consequent ones to belts of more erodible rocks Insequent valley: these are valleys which show no apparent adjustment to structural or lithological control CLASSIFICATION OF VALLEY

10. These valleys are classified on the basis of geologic structure: Homoclinal valleys: it is also known as strike valleys which follow beds of weaker rock along the flanks of folds Anticline valleys: these are valleys which follow the axes of breached anticlines Synclinal valleys: the axes of synclines Fault valleys: the streams follow depressions consequent upon faulting Fault line valleys: they are subsequent valleys following in fault line CLASSIFICATION OF VALLEY BASED ON STRUCTURES

11. cont’d.. F LUVIAL FEATURES: waterfalls & rapids pools; lakes canyons & gorges

12. A long, deep, narrow valley with steep cliff walls. It cut into the Earth by running water . It often having a stream at the bottom. CANYONS Colorado River of state : Arizona

13. A gorge is a steep, v-shaped valley formed by the vertical erosion of the land by the river. The Indus gorge in Kashmir is the deepest in the world(about 5180 m). If the region is arid where there is little weathering and mass wasting on the valley asides, the gorge will be impressively deep. If such a gorge is deep, long and u-shaped, we call it canyon. GORGE

14. Waterfall: a steep drop in the course of a river it has a high head of water and a characteristic plunge pool at the base waterfalls often form when a band of resistant rocks, Knick point : a sharp irregularity in a stream-channel profile, commonly caused by abrupt changes in bedrock resistance and at which waterfalls starts Plunge pool: also known as waterfall lake is a pool, lake, or pond that is small in diameter, but deep. Plunge pools can remain after the waterfall has ceased to exist or the stream has been diverted. Contd..,

15. Are depressions that are eroded in to the land rock of the streamed by abrasice action of the sediment load. When a stream is full, the swirling water can cause sand and pebbles to scour out smooth, cylindrical or bowl-shaped depression in hard rock Tend to form in spots where the rock is a little weaker than the surrounding rock.They may contain certain sand or an assortment of beautifully rounded pebbles. POTHOLES

16. Many tributaries have fed the river upstream. The volume of water increases and lateral erosion is taking place River channel has become much wider and deeper The surrounding valley has also become wider and flatter with a more extensive floodplain MATURITY STAGE

17. Bends or loops in the river One of the most distinctive features of the river in the middle course is its increased sinuosity Unlike the relatively straight channel of the upper course, in the middle course there are many meander (bends) in the river As water flows into a meander it take on a helical or spiral flow that determines where erosion and deposition is concentrated MEANDERS

18. Slip off slope: a small beach found on the inside of a meander bend where deposition has occurred in the low energy zone. River cliff- a small cliff formed on the outside of a meander bend due to erosion in this high- energy zone. When the water in an oxbow lake dries. An oxbow lake is a U-shaped lake water body formed when a wide meander from the mainstream of a river is cut off to create a lake. This landform is called an oxbow lake for the distinctive curved shape that results from this process. Contd..,

19. Final stage of a river is reached when the river is flowing on more or less flat surface. The speed so low that no net erosion occurs any more. Erosion on the slopes is balanced by deposition on the floodplains. Peneplain- a flat and relatively featureless landscape with minimal relief; considered to be the end product of the geomorphic cycle. Peneplain means “ almost a plain the process is known as peneplanation. From now on the rivers just sweep over the floodplain and rework the sedimement, creating various floodplain features. Isolated remnants of resistant bedrock may rise over the peneplain surface, the so called inselbergs. OLD STAGE

20. Contd..,

21. Alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. ALLUVIAL FAN

22. Old or mature stage landforms may be uplifted due to climate change or tectonic activity Entrenched meanders are the result Entrenched meander: a winding, sinuous stream valley with abrupt sides. Because the river is moving on a flat surface, deposits sediments at the bed often act as barriers to free flow of water making it to form meanders REJUVENATION

23. DRAINAGE PATTERNS Dendritic : Irregular branching pattern (tree like) in many direction. It is common in massive rocks and in flat lying strata Due to strong resistance of rocks headword development of valley is negligible. Parallel : Parallel or sub-parallel drainage formed on sloping surface. Common in terrain with homogeneous rocks. Development of parallel rills, gullies or narrow channels are commonly seen on gently sloping surface

24. Contd.. Radial: Streams radiates out from the center of the topographic high common in Volcanic terrain Rectangular: Channels marked by right-angle bends Commonly due to presence of joints and fractures in the massive rocks (or) foliation in metamorphic rocks.

25. Geomorphologic processes like fluvial, glacial, Aeolian, coastal, acts upon the earth bringing changes on the morphology of the earth. In these fluvial process plays an important role. Three stages of fluvial process, youth, maturity and old stages can be observed over a span of time. They create specific landforms like valleys, streams, flood plain, peneplain, canyon, alluvial fan etc. at different stage. Thus fluvial processes through much light on the previous geological events Conclusion

26. 2002-william D Thornbury-Principles of geomorphology- new age international publishers.282-297 G.B.Mahapatra; The Text Book of Physical Geology ;CBS publishers & distributors pvt.ltd; 214-242 Parbin Singh; General & Engineering Geology ; Katson Education Series; 56-80 www.wikipedia.com References