Influence of tides, bathymetry, lithology and regional flows on the salinization process in nature area the Rammegors

Ilja America,Perry De Louw,Sjoerd Van Der Zee,George Bier,A Szymkiewicz,A Sadurski,B Jaworska-Szulc

doi:10.1051/e3sconf/20185400001

Ilja America, Perry De Louw + Show 5 more

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https://doi.org/10.1051/e3sconf/20185400001

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Abstract

Nature area Rammegors, which has recently been transformed from a fresh inner-dyke nature area to a salt tidal area. Due to this transformation, salt water is infiltrating in a fresh waterlens. This salinisation process is investigated in more detail by two- and three dimensional models together with mearsurements in the area. Zeeland project FRESHEM has provided detailed isohaline maps of the area and Deltares is making transient isohaline maps based on measurements made by an ERT-cable which is situated in Rammegors. These data has been and will be used to investigate which factors; bathymetry, lithology, tides or regional groundwater flow, will have the largest impact on the salinization process in Rammegors. This investigation shows that discretization size has an influence on the speed and spatial distribution of salt plumes. Lithology has the largest influence on the salinization process, followed by bathymetry. Spring and neap tides do differ from the normal tides situation only when bathymetry is not taken into account.

Highlights

Rammegors was still an inner-dike nature reserve near the island of Tholen, wedged by the Scheldt-Rhine channel on the one hand and the Easternscheldt on the other, 40 years ago
In order to investigate how tides, bathymetry, lithology and regional groundwater flow influence free convection and salinization processes in nature area the Rammegors, a 2 dimensional model has been created in a generic MODFLOW/MT3DMS-based computer program, named SEAWAT in a GMS environment
The free convection plumes which are developed with a discretization size of 2 meter, are more emerged and broader than the plumes that were formed at smaller scales

Summary

Introduction

Rammegors (figure 1) was still an inner-dike nature reserve near the island of Tholen, wedged by the Scheldt-Rhine channel on the one hand and the Easternscheldt on the other, 40 years ago It took part of a dynamic tidal system consisting of deep channels, tidal flats and salt marshes (De Louw et al, 2016). In order to give this valuable nature more space, the connection between Rammegors and Easternscheldt is restored This creates a salt tidal area, where salt marshes can thrive again and birds can find food on the mud flats. The recovery of the original Zeeland landscape, but controlled behind a safe dike This MSc-study focuses on nature area Rammegors which experiences an unstable density stratification, as heavier seawater lies on top of lighter freshwater, since the connection with the Eastern Scheldt in December 2016. The unstable density stratification can give rise to free convection (fingering) were salinization occurs much more rapid because advective flow is driven by density differences (Post and Kooi, 2003)

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