Runoff and soil erosion from areas of burnt scrub: comparison of experimental results with those predicted by the WEPP model

The effects of burning on runoff and soil erosion from scrub-bearing hillslopes in northwest Spain were investigated by monitoring of experimental plots over a 4-year period. At the beginning of this period, two plots (BP1 and BP2) were subjected to low-intensity controlled burns, and two plots left as controls; in the year following the controlled burns, however, one of the control plots (plot WF) was burnt in a wildfire of higher intensity than the controlled burns. Runoff and erosion losses from the BP plots were only slightly higher than from the control plot, with the loss in no case exceeding 300 g m−2 yr−1. Erosion losses from plot WF were considerably higher (1314 g m−2 over the 1st year post-burning, 8.5 times higher than from the control plot). These results were compared with those predicted using the Water Erosion Prediction Project (WEPP) hillslope model (Version 95.7). In general, WEPP predictions of total runoff volume over the study period were acceptable: coefficients of determination for the regression of predicted on observed values were 0.41, 0.68, 0.66 and 0.57 for the control plot and plots BP1, BP2 and WF, respectively. Erosion losses were likewise predicted with reasonable accuracy, though the model showed a consistent tendency to under-estimate, particularly with plot WF.