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
 Classification 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
1) SOLUTION
2) SUSPENSION
3) SALTATION
4) 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. FLAT
FLOOD PLAIN

6. Alluvial Cones: slope angle(150) cone
shaped, porous sediments
Alluvial cone

8. 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
mountain
s
Coalesce of
aluvial cone
Base of the mountain

9. 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

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

11. Bends of longitudinal course of the rivers
The bend of meander have two types of
slope sides.
1. Cliff slope side - concave slope ,
channel strikes directly with severe
erosion resulting in to formation of
vertical cliff.
2. 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

12. Meandering Belt
Deposits -
Point
bar
Back
swamp
Natural
levee

13. 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

14. Deposits of silt and clay
laid down in the flood
basin back of natural
levees as water logged.

15. Low lying deposits during
flooding in late mature stage,
formed due to decrease in water
volume after flood.
Flat flood
plain

16. 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.

17. 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

18. 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.

19. Geological significance -1. In Palaeoclimate.
2. Study of Sedimentology
3. In Stratigraphy
4. In Economic Geology.
5. Barried channels are
source of water
Habitation around alluvial
cone in Dehradun

20. 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

21. References
 Thornbury william D., Principle of geomorphology
second edition , CBS publishers and distributors.
 Sam boggs jr. (1996), principle of stratigraphy and
sedimentology 2nd 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.

22. THANK YOU