Sedimentdynamics and resilience on tidal flats
Bagde, S. (2020). Sedimentdynamics and resilience on tidal flats. MSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 93 pp.
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| Abstract |
Background and Aims: Intertidal environments worldwide are of prime importance to biodiversity and coastal defence, acting as a natural buffer to global climate change and sea level rise. However, anthropogenic induced activities and rapid climate change place these environments under stress and risk of drowning, increasing the flood risk in the inhabited areas behind them. Sediment characteristics, biotics, tidal flat morphology and hydrodynamics are often interrelated and prime shaping factors of estuaries and tidal basins. Due to the plethora of processes combined with the expectation of enhanced sea level rise, quick measurable indicators predicting the systems’ future development are desired. This provides the option of restoring the system before reaching a critical tipping point. Theoretical approaches have shown that for systems where a decreased ecological resilience is observed, more time is needed to recover back to the state of equilibrium. This can theoretically serve as an early warning signal. This research therefore aims to determine whether this approach can also be applied to tidal basins, and if long-term behaviour can be explained by short-term recovery of the system.Methods: To account for a wide range of tidal flat characteristics, this research has been executed in two tidal basins in the Netherlands: The Eastern- and the Western Scheldt. The long-term dynamics are determined using satellite imagery over the last 30 years. The short-term tidal flat properties and dynamics are examined during multiple field campaigns. For determining the resilience of the system, the systems are disturbed, and their recovery regularly measured over time.Key Results: This research shows the significant importance of hydrodynamics from the impact of grainsize and inundation time. The tidal bed-level recovery was found to be in line with the phenomena of ‘critical slowing down’. Results also indicate the relations between the systems’ exposure to wind energy and long- and short-term behaviour. The state of sediment equilibrium of the system is also important for its response to disturbances. Sediment deficits account for quicker erosion, implying a closer proximity to reaching a critical tipping point in the future.Conclusions: This research provided insight in the improvement of predictions related to resilience of sediment dynamics in tidal systems. The complexity of the system in terms of their interrelatedness, is emphasised again. It is therefore recommended to build on this research, with measuring the recovery rate of the tidal flats, to monitor the change in resilience providing the possibility to intervene when the recovery rate shows indications of reaching a critical threshold. |
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