Wildfires devastate, each year, around 100 000 ha of Portuguese rural areas or more, (Pereira et al. 2005), most of which are forests. The frequency of forest fires is expected to remain the same or increase in the future, due to the nature of Portuguese forestry activities as well as to climate change with future scenarios foreseeing an increased occurrence of meteorological conditions propitious for fires (Pereira et al. 2006). These factors underscore the importance of evaluating and mitigating the consequences of wildfires.

In wet Mediterranean regions such as central Portugal, burnt areas experience an increase in runoff and erosion (Shakesby et al., 1993) with the associated risks for on-site land degradation and e.g. off-site floods. An effort to assess the soil erosion consequences of the 2003 forest fires was undertaken by the Portuguese Water Institute (INAG) using the Universal Soil Loss Equation (USLE). INAG's approach, however, has three main drawbacks:

1) USLE as a soil erosion model is inadequate for assessing short-term soil losses and, due to the lack of calibration data from recently burnt areas, can at best be expected to provide very uncertain long-term erosion estimates (Morgan, 2005)

2) it referred to immediate post-fire conditions but especially soil characteristics (e.g. soil water repellency) and vegetation cover tend to change rather quickly, including by post-fire intervention by landoweners

3) it referred solely to on-site effects, namely on individual hillslopes, neglecting erosion of the road and/or gully-channel networks as well as off-site effects due to the hydrological connectivity between catchment elements

Problem 1 and 2 are being addressed by the ongoing EROSFIRE I project (POCI/AGR/60354/2004). By testing the predictive performance of 4 erosion models, with USLE as the model-to-beat", against extensive field erosion measurements at plot-to-slope scale during the entire first year following fire, the EROSFIRE I project aims to develop a tool for erosion hazard assessment of individual hillslopes in recently burnt areas.

The present proposal aims to:

1) evaluate the EROSFIRE I tool in the sense of its applicability to other geographical areas, i.e. with different physical-environmental characteristics (e.g. geology, soils), distinct types of land cover (e.g. pine stands), different post-fire land management practices or, simply, different fire intensities. In addition, the new project will also address the effectiveness of selected soil conservation measures;

2) address problem 3 of the INAG method, by assessing the off-site effects of forest fires on soil erosion hazards and incorporating them in a spatially-distributed model-based tool for catchment-scale erosion hazard assessment.

The combined toolset of EROSFIRE I and II will contribute significantly to inform the managers of burnt areas on suitable land management practices to minimize the soil erosion impacts of wildfires in the lands under their care. It will also give relevant information to water resources managers on changed water flow rates and sediment loads traveling through rivers and into estuaries, therefore contributing to integrated watershed management in general.

Diana Catarina Simões Vieira
Researcher

Paula Alexandra Aquino Maia
Researcher