Case studies: Langeoog

Monitoring beach and shorface nourishments

The island of Langeoog, which serves as a coastal Building with Nature laboratory, is one of seven inhabited barrier islands situated along the East Frisian German North Sea coast (Lower Saxony, Germany). The islands beaches are highly dependent on complex natural variability in dynamics of sand transport at the island’s surf zone and across tidal inlets. Langeoog in particular has no hard coastal protection structures adjacent to its sandy beaches. Dunes are protecting areas from flooding, which cover settlements and the fresh water lens for the water supply system of the island. On Langeoog, approximately 4.5 million m³ of sand have been nourished since 1971 to ensure the protection of dunes, to bridge temporary sediment deficient phases resulting from temporally and spatially varying approaching of tidal shoals. In 2017 and 2018, a combined beach and foreshore nourishment was implemented on Langeoog.

Excursion to Husum, 2017

Method

The first step in the project was to comprise a shared transnational methodology to analyse all laboratories in a consistent way. As a result, various National Analyses Reports were brought together in a Co-Analysis Report to focus on performance monitoring of beach and shoreface nourishments.

Additionally for Langeoog, terrestrial and hydrographic measurements and hydrodynamic data were collected and analysed.

Results

Sand nourishments are successfully applied BwN measures to stabilise the beach since several decades, especially on Langeoog.

Sand migration on the beach can now be detected more clearly with the newly developed analysis methods in combination with the data gained from the monitoring program implemented during the project.  Uncertainties such as short-term morphodynamic changes (e.g. smaller shoals migrating to the beach) can hardly be detected with measurements, but can be observed by drone-based monitoring. In combination with analysis of long-term measurements, the results of the projecthelp to improve a new design for future BwN measures such asnourishments on the East Frisian Islands.

langeoog

Local context

The state of Lower Saxony is responsible for the storm surge protection and maintenance of the islands as a public task. The Lower Saxony Dike Law (NDG) forms the legal basis. The NLWKN is the responsible state agency. To protect the inhabited areas on Langeoogagainst flooding and erosion, the beach-dune system must contain a sufficient volume of sediment. The North-western and Northern part of Langeoog is only protected by dunes. Therefore, the dunes are of great importance for Langeoog. Due to the location close to the tidal inletwith a depth below NHN - 20 m, beach nourishments are chosen mostly to refill the beach sectionsdirectly.

Future research directions

  • The value of long-term and high resolution monitoring emphasises the need of ongoing measurement programmes to support BwN-solutions and to evaluate their effectiveness.
  • Results of the monitoring programme can be analysed further to support these findings by numerical models.
  • Use the ‘Source, Pathway, Receptor approach’ to get a better understanding of how nourished sediments spread along the coast.
  • The speed of the morphodynamic systems can be elaborated further in combination with the expected diffusion time of nourishments.

Documents

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