RECONECT Tamnava River Basin — Large-Scale Nature-Based Flood Risk Reduction

The Tamnava river basin (730 km², western Serbia, Kolubara District) was repeatedly devastated by floods in 1999, 2006, 2009 and catastrophically in 2014. It was selected as a pilot site under the EU Horizon 2020 RECONECT project (grant 776866, 2018–2021), implemented locally by the Jaroslav Černi Water Institute, to test whether nature-based solutions could substitute for or complement conventional flood infrastructure.
Researchers modelled four scenarios projected out to 2100: the existing protection system; a green scenario adding new retention ponds and floodplain restoration; a grey scenario raising levees and diverting flood discharge; and a combined green-grey scenario, alongside afforestation/reforestation and obstruction removal.
Modelled results showed flood area reduced by 20-27%, flood volume by 28-35%, and damage costs by 40-47%, depending on retention pond configuration. A cost-benefit analysis found afforestation/reforestation returned a benefit-cost ratio of 3.5 and retention ponds 5.6 once five co-benefits (carbon sequestration, biological pest control, habitat creation, air pollution reduction, education) were added — turning marginally-positive flood measures into strongly positive investments.
These figures come from published hydrological and economic modelling, not yet from monitored outcomes of constructed works; further scale-up depends on land acquisition and municipal follow-through beyond RECONECT's research phase.

Read the full analysis: http://www.reconect.eu/news-events/