Abstract: This article describes a new layout of side spillway that scatters water flow laterally into an existing parallel-arranged plunge pool to achieve energy dissipation. Hydraulic model tests and numerical simulations were used in the study focusing on analysis of hydrauliccharacteristics of the flow over spillway and the flow patterns in plunge pool. The results show that removal of one part of the sidewall at an appropriate location combined with a sloping pool bottom can provide a condition for a certain portion of the flow to fall laterally into the pool uniformly along its way. At the opposite sidewall of spillway, a circular-curve contraction is adopted and extends downstream up to its joint with the pool sidewall. This contraction helps the rest portion of flow to jet into the pool along a path over the lateral nappe. Thus, the total jet nappe takes a shape of “∩” and it is fully stretched and expanded, then dispersed up to its pool plunging location, so as to avoid excessive impact pressure on the pool bottom. This spillway layout can not only produce little affect on the normal running of plunge pool in the case of other releasing structures in operation, but make a full use of the rear part of the existing plunge pool for dissipation of more energy, which could lead to a great saving of project investment.