Real life coastal laboratory to develop short- and long term strategies for the protection and preservation of Schleswig-Holsteins Halligen
The Halligen are located off the North Sea coastline of Schleswig-Holstein, the most northern federal state of Germany. They are surrounded by the Wadden Sea which was added to UNESCO’s World Heritage List in 2009. The Halligen are small and low lying marsh islands that are inhabited by around 270 residents and most of them are involved in federal coastal protection activities. A Hallig essentially consists of the surface area that is frequently inundated and the artificially constructed dwelling mounds (hereafter referred to as Warften) that prevent people’s houses from flooding (see Figure 1).
Figure 1: An inundated Hallig during storm surge conditions. People’s houses are built on artificial mounds (Warften) which are individually designed to withstand storm surges (photo by LKN.SH)
Over the last centuries, the common impact of cultivation, subsidence, sea level rise (SLR) and storm surges caused massive land losses along the North Frisian coast. It has been estimated that around 100 Halligen have been destroyed over the last centuries and only ten of them have survived till present day (Quedens, 1992). At the beginning of the 20th century revetments have been established and since then, the Halligen are mostly stable in size but still frequently inundated. Previous research projects (e.g. Sahall, ZukunftHallig) concluded that the Halligen benefit from these inundations due to sediment deposition and the subsequent vertical accretion of the marshland. However, Schindler et al. (2014b) show that some of the existing revetments act like a barrier, partly hindering the sediment transport onto the Halligen. They also show that sea level increases were faster than the vertical accretion throughout the last century. The disequilibrium is expected to accelerate as future rates of SLR are projected to exceed the observed rates. As a consequence, the Halligen would more often or even permanently be inundated in the future. However, quantifying the accretion feedback is still a challenging task. SLR will also shift the extreme events to higher base levels and increase the hydrodynamic impact that promotes erosion and land losses. Furthermore, the Halligen represent an offshore barrier system protecting the mainland coastline from high wind waves and foreshore erosion. Hence, a sustainable protection of the Halligen also contributes to the coastal protection of Schleswig-Holstein’s mainland.
The overall aim of the research project is thus to develop sustainable coastal protection and management strategies for the Halligen. In the research project ZukunftHallig the applicants identified two different time scales that need to be addressed when developing such strategies, i.e. a) short-term protection measures for the residents that can immediately be implemented and b) long-term strategies enhancing the natural adaption capacity. The associated research questions are:
a) How to immediately protect the Hallig residents?
Addressing this question, the effectiveness of short-term measures will be assessed in the field (Living-Lab) considering suggestions that have been developed in the precursor project together with the Hallig residents. The close collaboration between researchers and residents established in ZukunftHallig allows us to test, promote and constructively discuss engineered, eco-friendly solutions.
b) How to increase the natural adaptation capacity of the Halligen to SLR?
Long-term strategies regarding the natural adaption to SLR and future agricultural management will be assessed using observed data and a combination of multiple-regression and numerical models enabling to estimate the causes and consequences of different measures (e.g. optimized revetment heights, operational modes of sluices, optimized agricultural management).
Further research aims at:
- Modelling the hydrodynamic forcing and its feedback on sediment transport
- Providing long term estimates (for the years 2030, 2050, 2080) of the sedimentation
- Providing optimized protection and management strategies for the Halligen
- Providing turbidity data and vertical accretion data for single storm surge events
- Understanding the contribution of vegetation to sediment accretion
- Acceptance by inclusion of the inhabitants (needs, expectations, experience) for a sustainable long-term protection of the Halligen
To reach these aims, detailed knowledge regarding the local conditions is needed. The project partners have a broad experience in the study area and most of them have already cooperated in the ZukunftHallig project. Building up on this knowledge and experience, four subprojects are incorporating social and natural sciences as well as governmental institutions and inhabitants:
Hallig-A: Assessing the impact of individual measures and development of strategies
Hallig-B (I+II): Assessing the individual coastal protection measures under real conditions (B I) and linkage between scientific concepts and social needs (B II)
Hallig-C: Assessing bio-geomorphic feedbacks between plants and sedimentation
Hallig-D: Measuring, assessing, and editing the turbidity
The interlinking of the subprojects is represented in Figure 2.
Figure 2: Interlinking of the subprojects
Start/End: 10/2016 – 09/2019
Funding: 995.991,- €
Coordinator: Research Institute for Water and Environment, University of Siegen (fwu)
- Institute for Hydraulic Engineering and Water Resources Management, RWTH Aachen University (IWW)
- Institute for Sociology of Technology and Organization, RWTH Aachen University (IfS)
- Institute of Biology and Environmental Sciences, University of Oldenburg (LÖK)
- Geoscience Center, University of Göttingen (GZG)
- Landesbetrieb für Küstenschutz, Nationalpark und Meeresschutz Schleswig-Holstein (LKN.SH)
Prof. Dr.-Ing. Jürgen Jensen
Research Institute for Water and Environment, University of Siegen
Paul-Bonatz-Str. 9-11, 57076 Siegen
Tel: +49 (0)271 740-2172
juergen.jensen [at] uni-siegen.de
Dr.-Ing. Arne Arns
Tel: +49 (0)271 740-2627
arne.arns [at] uni-siegen.de