Low-cost “buffer” structural measure for flooding risk reduction in irrigation reservoirs

Irrigation reservoirs (IRs) largely located off-stream are the great forgotten hydraulic infrastructures in comparison with the deeply studied dams. This research is mainly aimed at reducing the risk associated with IR-Breach floods in irrigation ponds through a novel and low-cost structural measure, named "buffer", which is in the risk element. This guarantees a maximum flood lamination at a breaching event as well as the minimization hydrograph peak. Therefore, a reduction of the potential hazard associated to these undesired events is produced. Methodology starts with the identification of flood hazard generating causes; then, a detailed/comprehensive numerical hydraulic simulation framework is performed through synthetic models of IRs with an analysis based on breaching events and slope "buffer" thresholds. Finally, the decision-making stage is developed. This crucial one involves the simulation, adaptation, and optimization of both the IR and the "buffer" to the lowest risk location. This is inspired/supported by the implementation of an IR-breach Digital Twin approach that involves the most likely breaching events modelling with/without "buffer" solution. In this way, the optimal design of the "buffer" as structural solution completely adapted to the IR site is achieved. Thus, it is possible to design an effective and economical measure for the identified hazard. This approach has been exemplified in two large Spanish IRs (320,000 and 201,000 m3 roughly). The general efficiency of "buffer" solution is found to be at 20 % of generating flooding risk reduction, with a maximum longitudinal slope of only 0.50 % (flat terrain), and without the need to implement additional structural measures. This approach may be taken as a soft and adaptive engineering solution for the optimal and safe design of IRs.