Check dams and sediment control: final results of a case study in the upper Corneja River (Central Spain)

PurposeThe sediment yield and erosion rate in an area can be estimated by calculating the volume of sediment retained by check dams. However, results can show unrealistic and imprecise conclusions if the sediment volume is not measured accurately, as tolerable erosion rates are usually below 10 t ha(-1)year(-1).Materials and methodsOur previous research developed a topographic method (the Sections Method) for measuring the sediment wedges created by check dams and the sediment yield with a high degree of precision to avoid the aforementioned problem. Until now, however, it had only been tested for a few check dams. Here, we present a final and complete analysis applying this method to 113 check dams in a granitic restored area in the upper basin of the Corneja River (Central Spain), under a continental Mediterranean climate, to estimate an accurate mean erosion rate over 50years, as well as the downstream influence of the check dams.Results and discussionOur results show that the check dams trapped 5365.93m(3) sediment, which represents a sediment export of 0.096tha(-1)year(-1) and a total sediment yield of 5.6tha(-1)year(-1). These values are significantly higher (>18%) than those obtained with other, simpler geometric methods currently in use, such as the Prism and Pyramid Methods, as we have already argued in previous papers. It is therefore important to take this issue into account. Moreover, we confirmed a number of morphological changes. As a result of the check dam effect, the slopes of the streambed are 11% lower than the original streambed slope, with a maximum reduction of up to 39%, leading to higher infiltration rates in the streambeds, lower energy waterflows, and flood lamination. Furthermore, the sediment wedges created a new land surface of over 5000m(2) permitting the development of agroforestry uses such as riparian woods, orchards, cropland, or pastureland.ConclusionsThese final results show that check dams were highly effective and played a positive role in retaining and controlling sediment.