Risk evaluation of flood control alternatives during earth-rock dam construction using the interval number method

Earth-rock dams often fail to meet the designed flood control standards during the construction stage, and the choice of flood season operation schemes strongly affects project safety risks and investment costs. However, in-depth research on the coordinated control of these two objectives is lacking. Moreover, the relevant evaluation process involves diverse professional domains, such as hydrology, engineering technology, and project costing. Experts from different files have varying levels of understandings of different evaluation indicators, which makes accurate value assignment difficult. To resolve the aforementioned problems, expert evaluations for each indicator are expressed in the form of interval numbers, and the collective opinions of the expert group are synthesized and converted into a single specific value by considering the minimization of the distance between different expert assigned values as the objective. On the basis of this approach, a safety-cost evaluation model for flood control schemes of earth-rock dams during the construction period is established. Considering the Qianping Reservoir in Henan Province, China as a case study, seven flood control alternatives are comprehensively evaluated. The results indicate that the cofferdam-based flood control scheme corresponding to a 100-year flood return period achieves the highest composite evaluation score, marking it the optimal solution. This method provides scientific decision support the construction of similar projects and enables the coordinated management of both safety and cost risks.