Delta

Illustration of delta and its characteristics.

1. Depositional Fluvial Landforms Delta’s

2. A delta is a Depositional Fluvial Landform in humid geomorphic region except for Nile delta of Egypt which is in arid region. A delta is a feature of deposition formed when a river flows into a standing body of water. Deposition occurs as the velocity drops on entering the standing body of water , this reducing the capacity and competence of the river bed load and suspended material are ‘dumped’. Delta’s

3. Delta forms when velocity drops as the river enters a standing body of water, typically this is at the coast as the river flows into the sea . Delta’s An example of a delta formed when a river flows into the sea in south west Greenland

4. Flocculation occurs as fresh water mixes with salt water- e.g where a river flows into the sea -(then called brackish water), and is the process by which tiny particles in suspension like clay and silt (which under normal fresh water conditions would likely never fall out of suspension) coagulate with the salt in the water by chemical reaction and become heavy enough to ‘sink’ and be deposited . Flocculation

5. Delta is a site of deposition Formation of a delta depends on the estuarine dynamics It also depends on the velocity of river In long term processes size & shape of a delta depends on rock characteristics, rate of erosion, rate of rainfall in the upper river basin and in the ways river flwos . Characteristics of Delta Singh, S, 2005

6. Deltas only form where rate of deposition exceeds rate of sediment removal. These conditions are likely where: The calibre of the load of the river is very large (therefore requiring a high amount of energy to keep in transport). The costal area into which the river dumps its load has a small tidal range and weak currents ; meaning there is limited wave action and therefore little subsequent transport of sediment taking place after its initial deposition allowing large deltas to form Suitable place in the form of shallow sea or lake shores Long courses of river; means long river system Relatively calm sea Pre-conditions for Delta Formation 1 Singh, S, 2005

7. Accelerated rate of erosion in the catchment area of the river Large amount of sediment supply Geologically inactive sea coast; means almost stable condition of sea bottom Pre-conditions for Delta Formation 2 Singh, S, 2005

8. Hyperpycual : The density of river water is greater than the sea water Homopycual : The density of river water is same as the sea water Hypopycual : The density of river water is less than the sea water Factors of delta Formation

9. Delta is a very complex depositional system including three morphological process i.e. fluvial, terrestrial and marine environment. Delta’s are usually composed of three types of deposit Topset beds: The larger and heavier particles are the first to be deposited as the river looses energy Foreset beds: Medium calibre particles travel a little further before they are deposited as more steep angled ‘wedges’ of sediment Bottomset Beds: The very finest particles travel the furthest before very low velocity/flocculation leads to their deposition Delta Morphology Singh, S, 2005

10. Delta Morphology

11. Classification of delta by dominance Wave dominated delta –i.e. Nile delta, Egypt Tide dominated delta –i.e. Ganges delta, Bangladesh, India Estuarine dominated delta –i.e. Mackenzia , Hudson delta Classification of delta by shape Arcuate –i.e. Ganges delta, Nile delta Birds Foot –i.e. Mississippi delta Cuspate –i.e. Ebro delta in Spain Delta classification

12. Delta type: Arcuate delta Tide dominated delta http://eol.jsc.nasa.gov/debrief/STS066/rep2.htm Ganges Delta, Bangladesh

13. NASA satellite image in false color Nile Delta, Egypt Delta type: Wave dominated delta Arcuate delta

14. http://earthobservatory.nasa.gov/IOTD/view.php?id=50500 River Deltas, Lake Ayakum , Tibet Delta type: Arcuate delta

15. Mississippi Delta Delta type: Birds Foot Jesse Allen, University of Maryland’s Global Land Cover Facility, andLANDSAT 1

16. Okavango Delta, Botswana Delta type: Arcuate delta Tide dominated delta http://www.flickr.com/people/8942661@N02

17. Colorado River Dry Delta http://gallery.usgs.gov/photos/10_15_2010_rvm8Pdc55J_10_15_2010_0#.Ur0mcvfTnrd

18. Web: Image [slide 12]: http://eol.jsc.nasa.gov/debrief/STS066/rep2.htm Image [slide 13] : NASA satellite image in false color Image [slide 13]: http://earthobservatory.nasa.gov/IOTD/view.php?id=50500 Image [slide 14]: Jesse Allen, University of Maryland’s Global Land Cover Facility, andLANDSAT 1 Image [slide 15]: http://www.flickr.com/people/8942661@N02 Image [slide 16]: http://gallery.usgs.gov/photos/10_15_2010_rvm8Pdc55J_10_15_2010_0#.Ur0mcvfTnrd Info: www.wikipedia .com www.slideshare.com Books: Singh, S; Geomorphology , Prayag Pustak Bhawan , 2005 Bibliography

19. Thank You