Impact of Sea Level on Ecosystem Dynamics of Salt Marshes

ISLED (Impact of Sea Level on Ecosystem Dynamics of salt marshes) part of the Eloise Project funded under DG XII of the European Commission.

Below is a summary of the project. A full PDF version of the report is available for download.

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L A B Coastal has been continuing the studies on erosion and accretion in three salt marshes on the north side of the Westerschelde estuary (The Netherlands). Studies in which rates of accretion or erosion are being tracked on a three monthly basis are carried out using a two metre bar which is set between pairs of fixed reference points. Changes in ground surface level relative to this bar are measured at 20 points along the bar.

A monitoring network has been established consisting of 30 transects in three different marshes along the Westerschelde (Ritthem, Ellewoudsdijk and Waarde). Preliminary results already show significant differences both within and between the marshes.

The deposition of sediment during a period of 24 hours is being studied by means of sediment traps which each consist of a 70 millimetre diameter glass-fibre filter paper attached to the sediment surface by four wire pegs. Similar size cellulose filter papers are positioned underneath them to ensure that only incoming sediment is retained by the glass-fibre filter papers. After exposure to two consecutive tides these glass-fibre papers are dried and weighed. Using the previously determined density of deposited sediment on a dry-weight basis the depth of the deposition is calculated for the two-tide period and, after allowing for the frequency of tides reaching the level of a particular set of sediment traps the annual rate of accretion was estimated as being between 17 and 20 mm/yr.

This was three times the accretion actually measured at Waarde and Ellewoudsdijk and eight times that at Ritthem suggesting that there had been substantial reworking of the sediment initially deposited, with much of the fresh sediment being removed by subsequent erosion.

Latest photos from the site

Investigation into sediment deposition on the salt marshes at Waarde	Assessing vegetation categories on the salt marshes at Waarde	Erosion of the cliff edge at Waarde