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Experimental physical modeling of tidal creek networks

Experimental physical modeling of tidal creek networks. Brigitte Vlaswinkel August 2004. Marine Geology and Geophysics Division Rosenstiel School of Marine and Atmospheric Science University of Miami. This week’s goal…. Build a tidal drainage network from scratch: Bidirectional flow

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Experimental physical modeling of tidal creek networks

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  1. Experimental physical modeling of tidal creek networks Brigitte Vlaswinkel August 2004 Marine Geology and Geophysics Division Rosenstiel School of Marine and Atmospheric Science University of Miami

  2. This week’s goal… Build a tidal drainage network from scratch: • Bidirectional flow • Very low gradient (6.10-4) Conform to the Reality??

  3. Miami South Florida Andros Island Study Locations

  4. © SpaceImaging Tidal Creek Networks • Digitized on IKONOS data and orthophoto quads • Analyzed in GIS

  5. Andros South Florida 2 km 5 km • muddy carbonates • microtidal, low energy • shallow creeks • juvenile mangrove • mixed carbonate / organics • mesotidal • deep creeks (3-6 m), more straight • mature mangrove forests

  6. Andros Island Bahamas

  7. Big Sable Creek Southwest Florida

  8. 1 km 1 2 Active networks 3 4 Stabilized networks

  9. 1 1 2 2 3 Horton (1945) stream numbering – fluvial channel segments Order 1 Order 2 Order 3

  10. Tidal Creek Segments Segment length by network – geographic context Andros Exponential distribution

  11. Segment length by network – geographic context South Florida (South) (North) Exponential distributions

  12. Tidal Creek Segments–Interpretation Exponential distribution: consistent with stochastic processes Inflection: change in probability distribution structure, change in processes?? Greater length of inflection = more shorter creeks

  13. Andros • Geographical influence.. • Change systematically from north to south • more abundant short creeks to south (probabilistically) • more later….

  14. Tidal Creek Network Structure Entropy: measure of network disorder rij = probability of transition from a stream of order i into one of order j. E = 0 indicates a perfectly ordered system (streams of order i flow only into streams of order i+1).

  15. E > 0 E = 0 E = 0 means perfectly ordered system E > 0 means disorder!

  16. Creek networks are less ordered towards the south… Andros

  17. Network Structure & Segment Length Composition Configuration Entropy (disorder) correlates with Abundance of short creeks southward Less order R2 = 0.94 More shorter streams Andros

  18. Conclusions • Different settings, but many statistical similarities exist between two tidal networks in terms of scaling, patterns and the exponential length-frequency distributions • Creek network metrics are consistent among networks within each area • Bottom line: both composition and configuration of creek networks are predictable (stochastically)

  19. Objectives • Create a tidal creek network with exponential length frequency distributions similar to drainage systems found along carbonate dominated shorelines • Observe and quantify (composition & configuration) the spatial and temporal development of the tidal creek networks • Observe and quantify the similarities and differences that occur during network elaboration using different scenarios of a tidal regime (e.g. tidal range, asymmetry) • Compare and contrast the results with morphometric studies carried out in South Florida and Bahamas

  20. Hypotheses Tidal networks evolve differently though time than river networks… Glock, 1931

  21. Hypotheses • Tidal range Rel. # of 1st order creeks • Vegetation density Width/depth ratio Max. channel depth • A break in the probability distribution structure of creek lengths reflects an abrupt change in processes • Similar morphometric patterns, even with different hydrology, substrate and vegetation density, suggest the influence of more universal processes and responses in the formation and evolution of tidal creek networks.

  22. References Rankey, E.C., 2002. Spatial patterns of sediment accumulation on a Holocene carbonate tidal flat, northwest Andros Island, Bahamas. Journal of Sedimentary Research, 51, p. 591-601. Rankey, E and Vlaswinkel, B., 2002. Morphometrics of carbonate tidal creek systems, Bahamas and Florida: Implications for tidal flat response to sea-level rise. Abstract and presentation at Geological Society of America Conference, Denver, Co, October 2002.

  23. My question to you With limited and what would be the most useful dataset to collect ? • Width/depth • Hydrology • Gradients

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