A simple design method for concrete fuse blocks at small dam spillways

Concrete fuse blocks are a promising cost-effective solution for enhancing small dam safety while increasing their storage capacity. This is especially needed in regions facing critical challenges due to limited water resources and the less rigorous design standards typically applied to small dams. Developed by the NGO HydroCoop, this technology is designed for installation on free-flow spillways. To enable large-scale implementation, a practical and safe design method is required—a method that is currently lacking. To address this gap, an analytical model was developed to predict the fuse block tipping head based on the physical stability of the block, and was validated with experimental data. Systematic tests were conducted at laboratory scale (1/10 scale factor) using six blocks with varying widths (dimension perpendicular to the flow direction). These blocks were tested in two configurations—alone on the weir or with adjacent blocks—and in two positions: at the center or on the side of the weir. The tests enabled the determination of the blocks’ tipping head. A standard block geometry was defined and used alongside the model to create a simple design table. This table allows practitioners to determine the appropriate fuse block height based on two input parameters—block density and head over the spillway crest—without requiring complex calculations. A dedicated discussion addresses the practical implications and limitations of fuse blocks, including the intensity of discharges generated when the blocks tip, the risk of earlier-than-expected tipping, and the usable storage range. Additional experimental validation is nonetheless needed to refine the method for non-standard geometries. A future research perspective is also to investigate the potential structural consequences of block tipping, both on the spillway and downstream.