Traditional water meadows (lameiros) buffer the increase in sediment transport caused by recurrent fires in Mediterranean headwater basins

The role of traditional water meadows located at the valley bottom ( lameiros ) on the process of sediment transport remains poorly studied, especially after forest fires. We quantified the spatiotemporal changes of sediment transport caused by recurrent fires in two transboundary (N Portugal, NW Spain) headwater paired basins (32 km 2 in total) where tens of fires affected vegetation (Mediterranean forest) between 1997 and 2020. The difference Normalized Burn Ratio (dNBR), the Aggregated Index of sediment Connectivity (AIC), and the Sediment Delivery Ratio (SDR) were calculated for ten temporal scenarios, and how the 99 lameiros modulate the sedimentological response. Overall, 49.8% of the study area burned at least once, with low- to moderate-low severity prevailing, but higher recurrence, up to four times, affected northern and higher-altitude zones. Vegetation recovery and human activities (new forest trails, firebreaks and post-fire management) occurred unevenly across scenarios. The shorter the distance to lameiros , the lower fire severity and frequency. Over time, AIC and SDR increased with the largest fire-affected areas and slightly decreased with vegetation recovery. At the small sub-basin scale ( n = 756; 549 burnt and 207 unburnt), lameiros reduced SDR by 36% and 7% in the burnt and unburnt sub-basins, respectively. Current soil erosion and sediment yield were of 3.34 and 3.96 Mg ha −1 yr −1 , and 322 and 344 Mg yr −1 in the two basins (calculated with RUSLE-AIC-SDR). Preservation, maintenance and restoration of lameiros should be prioritised as a nature-based and cost-effective solution that reduces fire propagation risk and soil loss. • Recurrent fires unevenly affect sediment connectivity/ delivery across the basins. • Half of the area burnt at least once, but high recurrence affected elevated zones. • The shorter the distance to lameiros , the lower fire severity and frequency. • Lameiros reduce SDR up to 36% and 7% in the burnt and unburnt sub-basins. • Lameiros act as a nature-based solution capable of reducing fire risk and soil loss.