Abstract The long-term morphodynamic response of estuarine systems to sea level rise and human interference has been studied using a Boolean network approach. The method uses Boolean variables to represent the different elements of the estuarine system, their inter-relationships and the external forcing. The response of a variable to a given change can be deduced from the corresponding Boolean function, which describes the feedbacks between that particular variable and the others in the network. This approach provides qualitative insights into the behaviour of estuary systems without the need for a detailed and quantitative specification of linkages between the various components of the system. Three types of estuaries: glacial valley, drowned river valley and drowned coastal plain are analysed and the results are compared. These estuary types are different in their origin and also have different characteristics due to the geomorphological elements present in each. Human interference, in the form of construction and dredging, has also been considered. An analysis of estuary systems shows that the nature of long-term morphodynamical response to sea level rise depends on the type of estuary and the availability of external sediment to meet the increasing sediment demand within the system. If the estuary has an abundant influx of external sediment on a continuous basis, then the estuary is able to maintain its geomorphology and reach a stable state. In the absence of adequate supply of external sediment, some of the prominent features such as salt marshes and spits are likely to recede or disappear altogether during the process of morphological evolution against sea level rise. Our analysis also suggests that the moderate human interference in the form of dredging and structural construction does not have a significant impact on the overall geomorphology of estuaries in the long-term. However, changes in intermediate evolutionary states can occur in response to such intervention, thereby showing short-to-medium term impacts on estuary systems.
D. Reeve, H. Karunarathna
Continental Shelf Research