Case studies: Gully Management

Shift from ore-debris lining to morphological relocation

Gully Management coastal lab investigates the desirability to shift shore protection management habits from using industrial ore-debris lining to morphological relocation of the gully undermining the dike. The investigation was oriented to the gully Vierhuizergat that is located near the dyke that protects the Marnewaard from the Waddensea.

Method

We analysed the pro’s and con’s to intervene in the Waddensea with different types of measures in order to prevent dyke undermining at locations where a tidal gully is moving towards the dyke. The lab’s activities were the preparations for a morphological intervention which  permanently relocates the tidal gully at a more remote distance of the dyke. A meticulous process approach was developed that permitted the consultation of stakeholders at each crucial process step in order to adjust the implementation strategy if necessary.

Results

More con's than pro's exist in adopting "soft" measures to protect the dyke from undermining by the gully. The ecological damage of more frequent interventions by soft measures is considered higher than the disadvantage of importing ore-debris from elsewhere. The uncertainty of the morphological stability of the sand supplements as a soft measure is a negative issue. This resulted from a modelling-- pilot. Evidence only can be obtained by practice. However, this would require full-scale morphological research, going beyond the  scope of developing a generic measure.

The current experiments at Vierhuizergat do not lead to the development of such general knowledge.

Local context

The Vierhuizergat gully is part of the Waddensea World Heritage Area. A lot of stakeholders contribute to reach its ecological goals. The ecological balances are considered as vulnerable to interventions.

Future research directions

• Research on soft measures viability of gully management at an appropriate location as a live experiment

Documents

All documents of the BwN project can be found at publications, below you find the documents belonging to this specific case study:

• Guidance Gully management (Dutch) (pdf, 1.3 MB)
• Verkenning Geulmanagement (Dutch) (pdf, 7.7 MB)
• Onderzoek geulmanagement (Dutch) (pdf, 5.7 MB)
• End report Gully management (Dutch) (pdf, 1.6 MB)
• Policy brief Waterboard Noorderzijlvest (pdf, 1.9 MB)