| Popis: |
With predicted climate change and sea level rise, the understanding of estuarine systems becomes more critical so as to gain an insight into the stability of the coastal environment both for environmental and economic reasons. The combined influence of tide and meteorological effects on the erosion, transport, deposition, consolidation cycle (ETDC) of intertidal sediment is not well understood. To further the knowledge into this area an intensive data collection program was conducted in the previously hydraulically un-investigated, macro-tidal estuarine lagoon at Pagham Harbour, Sussex. Monitoring of variations in the elevation of the mudflats indicate that generally accretion occurs in the west of harbour, with the east acting as source as well as a temporary storage area for the sediment which is primarily imported from the English Channel during winter storm periods. The redistribution of the sediment is dependant upon exposure to predominant wind direction, wind speed and local channel geomorphology. Monitoring of the water column identified that sediment is moved landward by means of a peak in turbidity which occurs at the beginning of each flood tide. This sediment movement is enhanced by tidal pumping caused by saline stratification which occurs at the onset of each flood tide as a result of a combination of the harbours' geomorphology and of the control of freshwater input. Precipitation during low tide causes eroded sediment to migrate towards the channels of the harbour, and the increase in freshwater discharge moves loosely consolidated sediment seaward. High freshwater events also retard the advancement of the saline water, prolonging the duration of the peak in turbidity. The magnitude of the peak is controlled by tidal range and recent precipitation events. Calibration of an "off the shelf coastal model highlighted the need for more data collection so that the accuracy of the prediction of the tidal curve, which directly influences depth and velocity, can be improved. Changes in climate and sea level are rendering coastal defences unsustainable, with management plans becoming outdated at an accelerating rate. Knowledge gained from these investigations can aid coastal manager to make more informed decisions for future management strategies in Pagham Harbour and at other coastal sites. |
