Wetlands International: First Sediment Build-Up Behind Dam

A year after Dutch and Indonesian partners began the restoration of the severely eroding coast in Demak and Semarang in Northern Java, the project is showing its first results.

Based on the principle of through Building with Nature, a sediment-permeable dam has been constructed and mangrove trees have been planted.

The first measurements show 45 centimeters of sedimentation. Behind one of the dams the mangrove seedlings are already emerging everywhere.

It is expected that if the dam structure stays in place, there can be a small forest in that area within a year or two. The mangrove forest should then take over the role of the dams and attenuate the waves and keep the sediment in place.

The project will run till 2020.

Evaluation of first year

The results of the first year are promising and the approach of Building with Nature is rapidly gaining in popularity.

During this first year, the project has been able to assess the condition of the coastline and the possible use of the Building with Nature approach for 8 villages, which is always site-specific and requires a thorough understanding.

In the most heavily eroded parts of the Demak coastline, this program is building permeable dams to attenuate the waves and trap the sediment.

This reverses the massive erosion and stimulates the natural re-growth of the mangrove greenbelt.

The program also has the intention to address the complex issue such as land subsidence as a result of extraction of ground water by industries, in particular at the rapidly eroding coast in the South, bordering the city of Semarang.

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