Tackling post-fire hydrological impacts and their management at different scales in Portugal

Abstract:

As in any other Mediterranean region, wildfires highly affect Portuguese forests leading to substantial economic and ecological losses. In addition, wildfires are an important cause for the degradation of ecosystem services provided by the forest, that are responsible for water quality, flooding, and soil erosion control. The use of adequate post-fire management practices is highly recommendable to mitigate such impacts. However, the dimension of the area affected by the 2017 wildfires in Portugal (500 thousand ha) showed the impossibility to effectively treat the entire burned area for erosion control. Therefore, hydrological modelling arose as a key–tool for post-fire land management decision making, identifying potential on-and-off-site post-fire impacts, allowing the selection of target areas with a higher soil erosion risk for the implementation of mitigation treatments.

To address this problem, the ESP team - under the FEMME project - defined the strategy of using soil erosion models at hillslope scale to address on-site impacts at the national level, and catchment scale models to address off-site impacts. A national soil erosion risk map in case of a wildfire will help land managers to choose the priority areas for the implementation of emergency stabilization measures. While continuous and event-based hydrological models, will allow assessing the risks of water quality degradation and the occurrence of extreme hydrological events, which can impact downstream values-at-risk.

This presentation will provide an overview of the work done at the national level with the Morgan-Morgan-Finney (MMF) model for the hillslope post-fire runoff and erosion predictions, the integration of SWAT and CE-QUAL-W2 models to address water quality impacts in the streams and reservoirs, and the use of OpenLISEM for event-based hydrological response predictions. At hillslope scale MMF is already calibrated to account for the application of mitigation measures such as mulch, while efforts are being made to implement those measures in burned areas using catchment scale models.