The article discusses a new type of a two-stage differential of the author’s design and the calculation of its design on an elastic base. The drop is designed to regulate the eroded sections of small rivers in the conditions of foothill zones. The proposed frame structure of the construction on an artificial gabion base allows solving the issues of stability, interaction of the structure with the flow and safe filtration under the structure. The bearing base of the drop is a system of cross reinforced concrete beams on an elastic base which allows the use of a method for calculating tape monolithic foundations. At the same time, an effective approach to the study of the stress-strain state of its load-bearing elements is proposed. Based on the results of the conducted studies, the tasks and calculation methodology for calculating its main parameters that ensure the reliability and efficiency of the entire structure have been determined for this two-stage differential.