Farmland near river confluences can mitigate flooding, study finds

Researchers from Tokyo Metropolitan University show that preserved agricultural land around river confluences can help mitigate flooding. They advocate for Eco-DRR, an approach that uses existing environmental resources to improve flood resilience.

The study is published in the journal Environmental and sustainability indicators.

The statistical analysis shows that municipalities with agricultural land in areas with high water storage potential experienced fewer floods, with a stronger correlation when agricultural land was located near river confluences. The team hopes their findings will inform efficient land use.

Climate change has led to an increased risk of extreme weather, of particular concern for flood-prone areas. As society seeks to address this unprecedented challenge, local authorities are scrambling to come up with the most effective measures to prevent and mitigate severe flooding.

One solution could be dams and barriers, but there is a limit to what can be achieved, particularly when weighed against their own ecological impact.

An alternative approach is Eco-DRR (Disaster Risk Reduction), an approach that seeks to use existing environmental resources, particularly agricultural land, to reduce risk. Agriculture is important to society in terms of food production, but it plays an important secondary role in reducing flood damage by absorbing and temporarily stopping large quantities of water. But its effectiveness depends largely on the location of agricultural land and how it is maintained.

Associate Professor Takeshi Osawa of Tokyo Metropolitan University is at the forefront of efforts to study the impact of Eco-DRR on disaster mitigation in Japan.

Japan is a particularly mountainous country, where maintaining large areas of agricultural land is difficult, with the migration of populations from rural areas to cities leading to the abandonment or urbanization of formerly agricultural land. It is therefore becoming increasingly important to understand the specific role that agricultural use plays in flood risk.

In his most recent work he has undertaken an extensive statistical analysis of the location of agricultural land in different municipalities in relation to local flood risks.

It analyzed flood damage surveys in 1,917 municipalities across Japan between 2010 and 2018, and looked at the amount of agricultural land located in areas with high water storage capacity. It found that municipalities whose land met these conditions had a lower risk of flooding.

Combining detailed geographic data, there is an even stronger link between the area of ​​agricultural land located at river confluences and reduced risk of flooding, stronger than the correlation found in agricultural land located in high potential areas water storage.

Confluence points between rivers exist throughout Japan and provide safe havens for a wide range of flora and fauna that can benefit from flooding. By combining food security, disaster mitigation and biodiversity, this presents a rare win-win scenario in the face of an increasingly challenging climate environment.