When the outlet of the spillway building cannot face the river and the topographical conditions are difficult to meet the pool length requirement of traditional bottom flow dissipation, increasing the pool depth and width to form a rectangular dissipation well is a feasible option. The shape of the rectangular dissipation well under varying incident water kinetic energy conditions was studied using a random forest algorithm bottom plate dynamic water pressure prediction model based on hydraulic modelling test data. The results show that the prediction model provides insights into the importance of the geometric boundaries of the rectangular dissipation well, ranking them in descending order as well depth, well length, and well width. Appropriate combinations of well depth and well length are provided for different Fourier number incident water flows, taking into account the optimal well width conditions. This ensures that the dynamic water pressure on the bottom plate meets the energy dissipation requirements. By analysing several groups of energy dissipation water volumes corresponding to the incident water kinetic energies (Fourier numbers), the study determines the minimum water volume required to achieve effective energy dissipation and identifies the optimum boundary values to achieve the energy dissipation effect.