Long-term Morphological Evolution of the Norderneyer Seegat

Long-term Morphological Evolution of the Norderneyer Seegat

Müller, J.M.

Stive, M.J.F. (mentor)
Wang, Z.B. (mentor)
Cleveringa, J. (mentor)
Oost, A.P. (mentor)
Noppen, J.P. (mentor)
Zitman, T.J. (mentor)
Niemeyer, H.D. (mentor)

Civil Engineering and Geosciences

2004-10

This study focuses on the consequences of sea level rise on the tidal inlet of Norderneyer Seegat, which is located in the East Frisan Wadden Sea. The Norderneyer Seegat is located between the islands of Juist and Norderney in the North and the East Frisian mainland coast in the South. The Wadden Sea landscape is mainly shaped by the tides. The tides constantly transport huge amounts of water and within sediments, which are gradually deposited, forming both sublitoral and intertidal shoals. The shoals performing intertidal flats are only visible during low tide. At low tide, the water recedes in narrow channels. These tidal channels work as a distribution system for water and sediment. The volumes of channels (water) and flats (sediment) are assumed to tend to a dynamically equilibrium state. A rising sea level disturbs this equilibrium. Due to the sediment import into the basin, the flats are continuously growing following the sea level rise. For most of the tidal basins of the Wadden Sea, the net amount of sediment transport into the basin is adequate to compensate the effects of the present rate of sea level rise (1,5 mm/year). If this would not be the case, the whole landscape of the Wadden Sea would change. This would have serious consequences for the safety of the coastline against the sea, because the intertidal flats effects a significant attenuation on incoming waves. To investigate if the system is capable to adapt to the changes with a sea level rise being significant accelerated compared to present conditions, the numerical model ASMITA (Aggregated Scale Morphological Interaction between a Tidal inlet and the Adjacent coast, Stive and Wang, 1996) is applied. The ASMITA modeling concept is based on empirical equilibrium relations between intertidal flats, tidal channels and the ebb-tidal delta performing the morphodynamic elements of the Wadden Sea area. The empirical equations implemented in ASMITA contain of empirical parameters. These parameters depend on regional properties. A part of the study is spent to the determination of these empirical parameters for the Norderneyer Seegat. To determine these parameters, topographic and hydrodynamic datasets are used provided by the Coastal Research Station on the East Frisian Island of Norderney (Germany). After calibrating the ASMITA model it is possible to calculate the development of the intertidal flats and the channels of the Norderneyer Seegat, due to an observed averaged sea level rise of about 1,5 mm/year. The calculations are limited to the volumes of the elements of intertidal flats and tidal channels. Using reconstructions of historical morphological states of this area for the years 1650, 1750 and 1860, which have been developed at the Coastal Research Station, the results of the ASMITA model, are validated. After reproducing the trends of the evolution in this area over the past 350 years, predictions can be made about the consequences of scenarios with an accelerated sea level rise. This aims to contribute to an estimate of the consequences of global climate change or land subsidence. At the end of the study, conclusions are drawn, about the consequences of a increase in sea level rise for the tidal inlet of Norderneyer Seegat. Therefore, different scenarios of sea level rise are simulated. Besides this, data analysis and modeling long-term developments of large-scale morphologies is discussed. The report is finalized with some recommendations and aspects to be studied in future.

http://resolver.tudelft.nl/uuid:18e68bbe-3719-4809-9c4a-8417b14ce155

TU Delft, Faculty of Civil Engineering and Geosciences, Hydraulic Engineering

Student theses

master thesis

(c) 2005 J.M. Müller