AbstractSoil erosion by water is a serious threat to crop sustainability and one of the main causes of landscape degradation in Mediterranean environments. The accurate assessment of soil erosion is a first requirement to face the problem of soil loss in highly fragile mountain environments. In this work, single flow (D8), multiple flow (MD) and combined flow (MDD) algorithms are used to compute cumulative runoff. Effective runoff is estimated after accounting infiltration and soil surface properties and added to the revised Morgan, Morgan and Finney (RMMF) model of soil erosion at the ‘Laguna Grande de Estaña’ catchment (Spanish pre‐Pyrenees). The combined flow algorithm explicitly associated to the gullies (MDD8‐G) leads to a more realistic assessment of runoff pathways. The MD algorithm generates unrealistic maps of concentrated runoff in gullies and overestimates soil erosion rates (average rate of 75 Mg ha−1 y−1). The D8 and MDD8‐G algorithms estimate similar values of soil erosion (average rates of 37 and 44 Mg ha−1 y−1, respectively). Paths, crops on steep slopes, open Mediterranean forest and sparse scrublands have the highest values of soil erosion (more than 50 Mg ha−1 y−1). The estimated rates with the MDD8‐G algorithm in control points in crops, forest and scrublands fit better with available data from 137Cs than those obtained with the D8 algorithm. Therefore, the MDD8‐G algorithm improves the quality predictions of soil erosion and is of interest to study processes of overland flow in Mediterranean environments with presence of gullies. Copyright © 2009 John Wiley & Sons, Ltd.