Risk Assessment North Coast Java: the conservation of mangroves should be top priority to maintain coastal integrity

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A new study by Deltares that assesses coastal flood risk for North Java states that the conservation of mangroves in rural areas should be top priority to mitigate flood risk and maintain coastal integrity mitigation of flood risk. In the long-run, limiting ground water extraction, bringing rivers back into the floodplain and using Building with Nature measures including protecting mangroves seem the most cost-effective strategies for the North Coast of Java. Only by doing this, loss of land and flooding can be mitigated along Javanese coastlines. In the more urban areas with less mangrove cover, other hybrid (green-grey) mitigation strategies may apply, integrated into a broader coastal management approach.

In this study, an area is considered under risk if intensity and probability of flooding are high and if many people or assets are potentially affected by the flooding. Hazards included in the study are storm surge and relative sea level rise, which can become more extreme as a result of climate change and man-made influences that cause land subsidence and ecosystem deterioration.

The study pinpoints high risk areas with the aim to inform strategic planning for coastal zone management. The flat and low lying coastal plain of Northern Java is very susceptible to subsidence and sea level rise and 2.5 million people are located in hotspots that with 0.5 to 1 meter subsidence can potentially flood with average storm surges. This is equivalent to 20% of the population of North Java.

The report was developed as part of the Building with Nature Indonesia project managed by the government of Indonesia, Wetlands International and EcoShape to support mainstreaming of the Building with Nature approach in Central Java and inform measures to mitigate and adapt to land subsidence. Globally, flood risk is challenging food and water security and economic development for millions of people.