Movie:WaveDelta

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Information Page: WaveDelta

Play Animation


CEM model of Ebro Delta



Key Attributes

Domain: coastal
Keywords: waves
Keywords: river flux
Keywords: coastline evolution
Model name: CEM
Name: Mark, Hannon
Where: Ebro Delta Spain
When: 55 model years


Short Description

Grade level: High (9-12), Under graduate (13-16), Graduate / Professional

Statement: formation of a wave dominated delta

Abstract: This animation is set up to mimick the evolution of a single channel delta forming into a marine basin with high wave climate. The incoming river sediment load goes very rapidly up over time (this is set up so as to simulate a change in climate, i.e. precipitation in the basin goes up). The parameter settings are not thought to be realistic necessarily, we are looking at an extreme case of change. Wave climate is defined as to have an incoming wave height of 1m, period of 6 s, asymmetry of incoming wave angles 0.4 (so a little weighted to the left), and a highness factor of 0.7 (higher proportion of unstable, >45 degrees, waves).

The Ebro delta is a very intriguing delta which, during recent centuries, has been controlled by both natural and man-induced factors. Deforestation of the Ebro drainage basin, by man, resulted in a fast progradation of the deltaic system until this century. Many dams were constructed along the river Ebro resulting in a drastically reduced river sediment discharge, with erosive processes now dominant in the shaping of the Ebro delta coastal area. In reality, the formation of the Ebro delta took place over 100-1000's of years.

Theory

A delta is formed by the interaction of three main controls: river energy, wave energy or tidal energy. Deltas are often classified by their morphological characteristics and the dominant controlling factor cinfluencing its morphology. An open ocean basin has a potential for high wave energy. High wave interference causes conflicted or deflected river mouths. There is less influence from fluvial sources. In wave-dominated delta regions, breaking waves cause immediate mixing of fresh and salt water. Typically, the fresh water flow velocity decelerates rapidly. A bar may form in the immediate vicinity of the distributary mouth, often supplemented by landward migrating swash bars. The wave action reworks the sediment, making it much sandier than other types of deltas. Alternatively, sediment is delivered by the river and but it is immediately transported along the coast. The sediment is then deposited as beaches and bars and the development of distributaries is limited. Dominant directions of wave approach can result in asymmetric beach ridges, and may cause the progradation of a spit across the river mouth. This results in channel flow oblique or parallel to the shore.

For the theory behind the models of this coupled river and wave-dominated coast simulations see the Model Help of the Coastline Evolution Model: https://csdms.colorado.edu/wiki/Model_help:CEM and the Model help of HydroTrend: https://csdms.colorado.edu/wiki/Model_help:HydroTrend

Links

References



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