Fluvial depositional landform geomorphology

Fluvial depositional landform geomorphology

1. DEPARTMENT OF APPLIED GEOLOGY DR. HARISINGH GOUR VISHWAVIDAYALA, SAGAR ( M.P. ) A SEMINAR ON Fluvial Depositional Landforms Under the Guidance of:- Presented By:- Prof. P.K. Kathal Varun Shastri Y18251028

2. CONTENTS Introduction Reasons of deposition C lassification of alluvial deposits. Alluvial fans and cones. Braided stream deposits. Meandering belt deposits. Point bar deposits. Back swamp deposits . Flood plain deposits. Natural Levee. River delta. Geological significance. conclusion

3. INTRODUCTION Stream deposition - Accumulation /deposition of loose transported material by stream in a basin. Fluvial Depositional Landforms – landforms either carved out due to erosion or built up due to deposition by running water. They are constructional landforms. CAPACITY of the stream is the total potential weight of sediment load which a stream can carry LOAD CARRIED BY RIVER A river carries load in FOUR forms SOLUTION SUSPENSION SALTATION TRACTION

4. Reasons of Deposition Break in slope. Obstruction in the channel. Spreading of water over large area. Decrease in volume and discharge of water . Contact with quiet water. Acceleration rate of erosion in catchment area. Supply of glacio -fluvial material. Supply of additional sediments by tributaries. Gradual increase load of sediments by rill and gully erosion.

5. DEPOSITONAL FEATURES Point bars PIEDMONT ALLUVIAL PLAIN FLOOD PLAIN DELTA CONVEX FLOODPLAIN FLAT FLOOD PLAIN NATURAL LEVEE ALLUVIAL FAN AND CONE Back swamp s

6. Alluvial Fans: Due to break in slope f an shaped, Alluvial material, flows down from mountain, accumulates at foot hills, streams enters into plain Alluvial Cones: slope angle(15 ) cone shaped, porous sediments Alluvial cone

7. Peidmont Alluvial plain Where closely spaced stream discharge from a mountain region across the piedmont. Their deposit coalesce at the base of the mountain to form a peidmont alluvial plain, e.g. Indo- Gangetic plain on the southern peidmont of Himalayas The Canturbury plains of NZ mountains Coalesce of aluvial cone Base of the mountain

8. Braided Stream Deposits - Depositional forms flow divides into a series of braids separated by islands or bars Braided channels tend to form where (1) Stream load is high; (2) Break in the channel gradient

9. Braided River, Nubra , India Kosi river course Sorrow of the Bihar

10. Meandering Belt Deposits - B ends of longitudinal course of the rivers The bend of meander have two types of slope sides . Cliff slope side - concave slope , channel strikes directly with severe erosion resulting in to formation of vertical cliff . Slip-off slope side - convex slope , deposition mostly of sand and gravel but sometime alluvium is also deposited, gentle slope. Abandoned meanders become Ox-bow lakes, filled by clays

11. Meandering Belt Deposits - Point bar Back swamp Natural levee

12. Point bars Found on convex side of meander, grow by individual increment, surrounded by water . Point bar Abandoned channel filling Filling of former channels during flood. Point bar Abandoned channel filling

13. Back Swamp Deposits - Deposits of silt and clay laid down in the flood basin back of natural levees as water logged .

14. Flood Plain Deposits - Low lying deposits during flooding in late mature stage, formed due to decrease in water volume after flood . Flat flood plain Convex flood plain

15. Natural Levees Low ridges, formed on both sides of a river channel by the accumulation of sediments, highest near river and sloping apart from it.

16. Delta Occur where stream hits slow water Suspended load is dropped Deposits build out into lake or sheltered sea, extending the length of the river Consists of three types of beds Topset beds - horizontal, surface delta Foreset beds - delta slope Bottomset beds – horizontal, bottom sea

17. Delta Abandoned delta lobes are sediment-starved. Sediments deposited before avulsion slowly subside. Compaction and dewatering. Decay of organic matter. Lack of sediment nourishment. Eventually, abandoned delta lobes are submerged.

18. Geological significance - In Palaeoclimate . Study of Sedimentology In Stratigraphy In Economic Geology . Barried channels are source of water Habitation around alluvial cone in Dehradun

19. Conclusion Fluvial depositional landforms are constructional or positive landforms cover smaller area on earth surface than erosional features. Give no information about recent diastrophic history as erosional landforms . These landforms low relief than erosional landforms. Used for cultivation

20. References Thornbury william D., Principle of geomorphology second edition , CBS publishers and distributors. Sam boggs jr . (1996), principle of stratigraphy and sedimentology 2 nd edition, apperentice hall publication. Siddharta k., The earth dynamic surface. A text book on geomorphology, kisalaya publications pvt . Ltd. Dr. Savindra singh , geomorphology, prayag pustak bhawan .

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