The paper considers the intensification of mudflow activity on the dumps of the Listvennichnyi quarry near the city of Yuzhno-Sakhalinsk. Eight cases of anthropogenic mudflows initiated by rainfalls were recorded during field observations conducted from May to November in 2020. First for Sakhalin, mudflows were recorded by video equipment. Parameters of mudflows were measured during their descent. Velocity values were obtained for six mudflows and compared with the values calculated by different methods. Mudflow pressure values were also calculated for all six flows. The derived values are in the range between 0.0044 and 0.0089 MPa. Different methods for the assessment of mudflow effects on objects depending on the pressure value were compared. The amount of precipitation sufficient for triggering anthropogenic mudflows is provided in the paper.