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Modelling soil erosion after wildfire in NW Spain: Advances and gaps
Cristina FernándezCentro de Investigación Forestal-Lourizán
Xunta de GaliciaSpain
Erosion Modelling Workshop-JRC Ispra, 20 March 2017
2
50 % of the burntarea in Spain
Post-fire erosion is a particularly critical issue in NW Spain because of the large number of fires that occur annually (an average of 8,000 per year in the period 2001-2010). Soil characteristics and the high rainfall erosivity potential…
lead to the post-fire soil erosion potential in the region being the highest in Spain…
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Verin
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Oia III
Oia II
Ponte-Caldelas III
Muros
Oia IV
Oia I
Cotobade
Ponte-Caldelas I
Negreira
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Ponte-Caldelas II
Pindo
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Vegetation cover six months after fire
Soil losses six months after fire as percentage of annual losses
Precipitation accumulated six months after fire
Soil losses concentrated in the first months after fire (> 80% in the first 6 post-fire months).
In that period vegetation cover is ineffective for soil protection.
The high population density in the urban-wildland interface area in the region magnifies thepost-fire erosive risk…
Since 2010, the Galician Forest Service is implementing rehabilitation plans to mitigate the erosive and hydrological impact of wildfires, including emergency soil stabilization actions in severely burned areas. Main objectives are:
• Mitigation of the threaten to the human life and resources
• Reduction of soil erosion
• Limitation of soil degradation
• Reduction of flood, debris flow and mudflow risk.
• Accelerate natural regeneration of the ecosystem
Remote sensing evaluation
Prioritization of areasto be treatedHydrologic models of runoff
and peak descharge flow
Field evaluation
Human lifeWater resources
Ecological resourcesProductive resources
FacilitiesCultural heritage
Fire severity indicators(vegetation + soil)
Valorization of threatened resources
Fire severity assessment
Soil and vegetationcharacteristics
Site climatecharacteristics
Wildfire documents
Hydrologic anderosion risk
Pre-planning
Treatment selection and application
Monitoring
Thematic digital mapping
Soil erosion models
Vega JA, Fontúrbel MT, Fernández C, Arellano A, Díaz-Raviña M, Carballas T, Martín A, González-Prieto S, Merino A, Benito E. 2013. Acciones urgentes contra la erosión en áreas forestales quemadas: Guía para su planificación en Galicia. Santiago de Compostela.
For the prioritization of areas to be treated, accurate soil losses predictions are critical:
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Observed values (Mg ha-1)
PESERA
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RUSLE
The performance of these models in burned soils is poor.In both cases, the correlations between the predicted and measured sediment yields
were quite low.
Fernández, C., Vega, J.A., 2016. Evaluation of RUSLE and PESERA models for predicting soil erosion losses in the first year after wildfire in NW Spain. Geoderma 273, 64-72.
SE =0,0004 *exp (0,7284 SBSI) *P * LU
Erosion 0.2-52 Mg ha year ;precipitation 674-3187mm; soil burn severity index 1.8-4.7; land use factor 1-3;
slope 20-53% ; soil depth 0.20-0.69 m; stoniness: 0.3-43%
SE =0,0004 *exp (0,7284 SBSI) *P * LU
Soil burn severity levels
1- Very low
2- Low
3- Moderate
4- High
5- Very high
Fernández, C., Vega, J.A., 2016. Modelling the effect of soil burn severity on soil erosion at hillslope scale in the first year following wildfire in NW Spain. Earth Surface Processes and Landforms 41, 928-935.
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Validation of that model yielded acceptable results. It seems that could be analternative for soil losses prediction the first year after fire in NW Spain
Some research gaps have arisen:
-Sediments response at cathment scale. Spatial distribution/Connectivity.-Climate change predictions: Changes in annualrainfall distribution?-Links between soil burn severity and firebehaviour need to be better defined/established.-Introduction of uncertainty in the models: probability of high soil burn severity & post-fireadverse meterorological events occurrence
