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(3) Impressum Jointly published by x The Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management (Bundesministerium für Land- und Forstwirtschaft, Umwelt und Wasserwirtschaft) and x Institute of Water Management, Hydrology and Hydraulic Engineering, Department Water-Atmosphere-Environment, University of Natural Resources and Applied Life Sciences, Vienna (Institut für Wasserwirtschaft, Hydrologie und konstruktiven Wasserbau, Department Wasser-Atmosphäre-Umwelt, Universität für Bodenkultur, Wien) Cover photos: from upper left to lower right (1) © Government of Styria; (2) © Seggau Castle; (3) © Tourism Association ““Südsteirische Weinstraße””; (4) © Joanneum Research Graz Editing: Hubert Holzmann, Reinhold Godina and Gabriele Müller Layout: Klara Stangl ISBN 978-3-900962-90-6.

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(8)   Thepapersincludedinthisvolumewerereproducedfromthemanuscriptversion submittedbytheauthors.Thepaperswereacceptedastheyweresubmitted.Only minorlayoutreǦarrangementswerecarriedoutduringediting.  TheEditorsandtheOrganizingCommitteetakenoresponsibilityforanyerrorand omissionorfortheopinionsoftheauthors.    . II.

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(41) RUNOFF AND EROSION IN A SMALL BURNT CATCHMENT IN CENTRAL P ORTUGAL. Runoff and erosion in a small burnt catchment in central Portugal Vieira D.C.S.1,*, Keizer J.J.1, Nunes J.P.1, Fernandes I.A.C.1, Faria S.R.1, Ferreira R.S.V.1, Varela M.E.T.1 & Pereira L.M.G.2 1 Centre for Environmental and Marine Studies (CESAM), Department of Environment and Planning, University of Aveiro, Aviero, Portugal 2 Águeda Higher School of Technology and Management (ESTGA), University of Aveiro, Aviero, Portugal * dianac.s.vieira@ua.pt. INTRODUCTION Post-fire erosion is a major concern because of its potential effects on soil and water resources. Wildfire is frequently observed to increases soil erosion rates (Shakesby and Doerr, 2006). Many studies have emphasized the role of the partial or entire elimination of vegetation and ground cover (thereby exposing the mineral soil to direct impact of raindrops and overland flow) as a key factor in the increased soil losses. Also fire-induced changes in topsoil properties like total porosity (e.g. Neary et al., 2005) and water repellency (e.g. Keizer et al., 2008a) can enhance overland flow and the associated transport of soil particles. Existing process-based erosion models like e.g. WEPP (Nearing et al., 1989) and EUROSEM (Morgan et al., 1998) can successfully simulate the effect of vegetation on soil losses in individual storms but their complexity often limits their usefulness for non-academic purposes. Therefore, empirical models such as USLE (Wischmeier and Smith, 1978) continue to be widely used. For example, the Portuguese national Water Institute (INAG) applied USLE to the 300.000 ha of rural areas affected by wildfires during the summer of 2003. However, the model’’s suitability for burnt areas (as opposed to the agricultural areas for which USLE was originally developed) was not supported by field observations. The present work concerns the EROSFIRE-II project (PTDC/AGR-CFL/70968/2006), which has as overall aim to assess the suitability of selected models for predicting soil erosion in recently burnt forest areas in Portugal. The proposed presentation will focus on the evaluation of the revised Morgan-Morgan-Finney model (MMF; Morgan, 2001) against slope-scale measurements of overland flow and/or erosion during the first year after fire. Earlier studies reported this model to perform satisfactorily in forests and shrublands in the humid areas of the north-eastern Iberian Peninsula (Keizer et al., 2008b; Fernández et al., 2010). The hydrological and erosion response at the catchment scale will be modeled with MEFIDIS (Nunes et al., 2005) but that is beyond the present scope.. STUDY AREA A forest area of about 60 ha located near the village of Colmeal, central Portugal (Figure 1) was instrumented following a wildfire that occurred during August 2008, and has been monitored at 1-2 weekly intervals from the end of September 3008 onwards. The land cover in study area consisted of commercial tree stands of eucalypt (Eucalyptus globules) and Maritime Pine (Pinus Pinaster). The soils in the area are classified as Cambisols and are shallow soils overlying schists, Mean annual rainfall is around 1250 mm but the rainfall during the study period only amounted to 900 mm.. ERB2010-CONFERENCE. 5-8 SEPTEMBER 2010; SEGGAU CASTLE. 119.

(42) VIEIRA D.C.S., KEIZER J.J., NUNES J.P., FERNANDES I.A.C., FARIA S.R., FERREIRA R.S.V., VARELA M.E.T. …. Figure 1 –– Location of the study area.. DATA COLLECTION AND FIELD MEASUREMENTS Five hillslopes were instrumented with slope-scale runoff plots as well as sediment fences, whereas a further five hillslopes were equipped with sediment fences only. A catchment of about 10 ha in the central part of the burnt area was instrumented with an H-flume and a gauging station comprising an automated rainfall gauge, a water level sensor, a turbidity sensor and an automatic sampler. Figure 2 gives an overview of the instrumentation. Additional work carried out in this study area includes: a. generation of high-resolution Digital Terrain Models using digital aerial photography and terrestrial laser scanning; b. recovery of the vegetation following fire and logging, with a special emphasis on the role of germination; c. direct and indirect wildfire effects on topsoil physic-chemical properties, in particular water repellency, organic matter content and composition; d. effectiveness of hydro-mulching to reduce overland flow generation and/or sediment losses; e. the eco-toxicological effects of ash-loaded runoff; f. nutrient losses by runoff at the hillslope to catchment scale.. 120. 5-8 SEPTEMBER 2010; SEGGAU CASTLE. ERB2010-CONFERENCE.

(43) RUNOFF AND D EROSION IN A SMALL BUR RNT CATCHME ENT IN CENTR RAL P ORTUGA AL. Figgure 2 –– Instrrumentation of o the study area a. PRELIMIN NARY RESU ULTS A first analyssis of the runooff and erosionn rates observved during thee first five moonths followinng the wildfiree suggested ann all but straigghtforward hyydrological annd erosion reesponse. Pron nounced diffeerences were found betweeen individuaal hillslopes as well w as betweeen an initial dry period and the subsequen nt rainy period. The differeences between n the slopes aree illustrated in Figure 3, deppicting the runnoff results at the micro-plo ot scale (< 1 m2) m for the firrst hydrologiccal year. Thesee results are preeliminary, how wever, and include isolatedd events with runoff r coefficcients above 1100%. These latter l events inn particular neeed to be revieewed carefullly for possiblle measuremeent errors as well w as for thhe possible co ontribution byy subsurface floow.. B Bounded plo ot Runnoff measuremen m nts 0 140 0. 20. Runnoff (mm). 60. 100 0. 80 80 0. 100 120. 60 0. 140. 40 0. Rainfall (mm). 40. 120 0. 160 20 0. 180 200 Se t -0 9. Ag o -0 9. Ju l-0 9. Ju n-0 9. 9 Ma i -0. Ab r-0 9. Ma r-0 9. Fe v-0 9. Ja n-0 9. De z -0 8. No v -0 8. Ou t-0 8. Se t -0 8. 0. Date. R Rainfall B BP3 B BP8. Figure 3 –– Rainfall and d runoff of miicro-plots during the first year followin ng wildfire. ERB2010-CON NFERENCE. 5-8 SEPTEMB BER 2010; SEGG GAU CASTLE. 1221.

(44) VIEIRA D.C.S., KEIZER J.J., NUNES J.P., FERNANDES I.A.C., FARIA S.R., FERREIRA R.S.V., VARELA M.E.T. …. REFERENCES Fernández C, Vega J A, Vieira D C S. 2010. Assessing soil erosion after fire and rehabilitation treatments in NW Spain: Performance of RUSLE and revised Morgan––Morgan––Finney models. Land Degradation and Development 21: 74-87. Keizer J J, Doerr S H, Malvar M C, Prats S A, Ferreira R S V, Oñate M G, Coelho C O A, Ferreira A J D. 2008. Temporal variation in topsoil water repellency in two recently burnt eucalypt stands in north-central Portugal. Catena 74: 192-204. Keizer J J, Nunes J P, Palacios E, Beekman W, Malvar M C. 2008b. Soil erosion modeling for two recently burnt eucalypt slopes: comparing MEFIDIS, MMF and USLE. In: ISCO2008, 15th Conference of the International Soil Conservation Organization. May 18-23, Budapest, Hungary. Morgan R P C. 2001. A simple approach to soil loss prediction: a revised Morgan––Morgan––Finney model. Catena 44: 305––322. Morgan R P C, Quinton J N, Smith R E, Govers G, Poesen J W A, Auerswald K, Chisci G, Torri D, Styzcen M E. 1998. The European Soil Erosion Model (EUROSEM): a dynamic approach for predicting sediment transport from elds and small catchments. Earth Surface Processes and Landforms 23: 527––544. Nearing M A, Foster G R, Lane L J, Finkner S C. 1989. A Process-Based Soil Erosion Model for USDA-Water Erosion Prediction Project Technology. American Society of Agricultural Engineers 32: 1587-1593. Neary D G, Ryan K C, De Bano L F. 2005. Wildland fire in ecosystems. Effects of fire on soil and water. Gen. Tech. Rep. RMRS-GTR-42-vol 4. Ogden, UT: USDA Forest Service, Rocky Mountain Research Station. Nunes, J.P., Vieira, G.N., Seixas, J., Gonçalves, P., Carvalhais, N., 2005. Evaluating the MEFIDIS model for runoff and soi erosion prediction during rainfall events. Catena, 61 (2-3): 210-228. Shakesby R A, Doerr S H. 2006. Wildfire as a hydrological and geomorphological agent. Earth-Science Reviews 74: 269-307. Wischmeier W H, Smith D D.1978. Predicting rainfall-erosion losses- a guide to conservation planning. Agriculture Handbook. Nº537. USDA. Washington, D.C; 58.. 122. 5-8 SEPTEMBER 2010; SEGGAU CASTLE. ERB2010-CONFERENCE.

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