Holocene water level changes in the Rhine-Meuse delta as a function of changes in relative sea level, local tidal range, and river gradient

Abstract

Published time-depth data from peat-covered slopes of early Holocene river dunes in the Rhine-Meuse delta are reviewed in the light of a new sea-level graph by Jelgersma. It is argued that the irregular convergence of the river-dune data on this curve with time can be explained in terms of a gradually decreasing gradient of the (tidal) rivers and a variable reduction - both in time and space - of the tidal range behind the coastline. A curve is constructed for the Brandwijk-Hazendonk area and shows the decrease of the raising effect of the river gradient on the local mean high-water level or groundwater level with time. For each time-depth point from the Brandwijk-Hazendonk area this gradient-effect reduction curve allows an estimate of the extent to which the decrease in tidal amplitude behind the coastline has compensated the gradient effect.