1 / 25

River-dominated deltas

River-dominated deltas. River-dominated deltas are often shaped like a bird’s foot. River-dominated deltas are dissected by numerous distributary channels. River-dominated deltas protrude far from the coast. Sediment in river-dominated deltas accumulates in shore-perpendicular ridges.

lindsey
Download Presentation

River-dominated deltas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. River-dominated deltas • River-dominated deltas are often shaped like a bird’s foot. • River-dominated deltas are dissected by numerous distributary channels. • River-dominated deltas protrude far from the coast. • Sediment in river-dominated deltas accumulates in shore-perpendicular ridges.

  2. Mississippi Delta http://www.ces.clemson.edu/semaps/la/nogu-a.jpg

  3. Wave-dominated deltas • Wave dominated deltas tend to be triangular in shape. • Wave-dominated deltas do not have many distributary channels. • Wave-dominated deltas do not protrude far from the coast. • Sediment on wave-dominated deltas accumulates in shore-parallel ridges and bars.

  4. Nile Delta http://www.elknet.pl/gsi/galerie/nil-delta.jpg

  5. Tide-dominated deltas • Tide-dominated deltas tend to be triangular. • Tide-dominated deltas have poorly defined, interconnected distributary channels. • Tide-dominated deltas do not extend far from coast. • Sediment accumulates in shore-perpendicular linear islands and ridges.

  6. Ganges Delta http://rst.gsfc.nasa.gov/Sect17/BNGFLD5x5.jpg

  7. Fraser River delta

  8. Controls on Delta Plan Form • Mode of mixing between inflow and basin waters • Post-depositional processes

  9. Mixing and Delta Form • Mixing decelerates inflow. • Deposition occurs where mixing occurs.

  10. Delta shape • Birdsfoot deltas occurs on coasts with slow mixing of inflow and basin waters and limited depositional reworking. • Triangular deltas are evidence of rapid mixing and extensive sediment reworking.

  11. Distributary Channels • Distributary channels are numerous where post-depositional reworking does not remove sediment from river mouth. • Wave-dominated deltas therefore have few channels, but river-dominated deltas have many.

  12. Delta Protrusion • Deltas protrude far from the coast where post-depositional reworking is limited. • Wave-dominated and tide-dominated deltas do not protrude from coast, and river-dominated deltas do.

  13. Orientation of Sediment Bodies • Waves produce shore-parallel bars. • Currents favour shore-perpendicular deposition. • Wave-dominated deltas have shore-parallel sediment bodies, and river- and tide-dominated deltas have shore-perpendicular bodies.

  14. Mississippi Drainage Basin http://www.mvn.usace.army.mil/pao/bro/MRivDrainageBasin.gif

  15. http://www.esl.lsu.edu/demos/modis/modis-diversions-highres.jpghttp://www.esl.lsu.edu/demos/modis/modis-diversions-highres.jpg

  16. Mississippi Lobes Coleman, J. M. (1988). GSA Bulletin, v. 100, pp 999-1015.

  17. New Orleans http://www.visit-new-orleans.com/visit-new-orleans-4.jpg http://www.globalsecurity.org/military/facility/images/new-orleans-fig12-1.gif http://www.victorsfinearts.com/images/newart/large/new%20orleans.jpg

  18. Goals of River Control • Correct, permanently locate and deepen the main channel • Prevent floods

  19. http://www.mvn.usace.army.mil/pao/bro/mrc_map.gif

  20. Mississippi Bay Fills Coleman, J. M. (1988). GSA Bulletin, v. 100, pp 999-1015.

  21. Evolution of a Bay Fill Coleman, J. M. (1988). GSA Bulletin, v. 100, pp 999-1015.

  22. River Control Problems • Continued maintenance of main channel has led to significant accumulation of sediment at mouth. • Water levels rise more dramatically during floods due to shallower gradient of river.

  23. River Control Problems • Levees must be built continually higher to protect against breaches and spillovers. • Land adjacent to main channel is starved of sediment. • Subsidence is causing severe coastal erosion.

  24. Summary • Deltas form where river-derived sediment accumulates faster than it can be dispersed. • Delta profile depends strongly on the density contrast between inflow and basin waters.

More Related