The principle theme of this study is to introduce a novel countermeasure to reduce the energy of the overflowing floodwater by utilization of a water cushion. For this purpose, laboratory experiments including “LW” cases (levee with water cushion) and “OL” cases (only levee) were conducted to elucidate the role of a water cushion in the flow structure variation after a levee is overflowed and to reduce energy. A moat (a deep and wide trench) with varying non-dimensional length (L_m* = L_m/h_L; L_m is the length of the moat where h_L is the levee height) and depth (D_m* = D_m/h_L; D_m is the moat depth) acting as a water cushion was provided at the toe of a levee with varied landward slopes (S_L). The energy reductions in the LW and OL systems were found to be very close to each other at lower overflow water depths, while it was 25% greater in the LW system than in the OL system at higher overflow water depths. Changes in the landward slope (S_L) of the levee, non-dimensional length (L_m*), and depth (D_m*) of moat significantly changed the flow structure and created six different flow structures. However, 1–6%, 1–3%, and 1–5% differences in energy reduction rate were observed by varying S_L, L_m*_, and D_m*, respectively, in LW cases. All flow structures contributed greatly to energy reduction, but the energy reduction rate was maximum in flow structure named as T-2. Flow structures named as T-2 and T-6 are preferable due to increased water depth inside the moat and presence of submerged hydraulic jump which can be achieved during landward slopes S_L = 1:1, 1:2 and by decreasing L_m* D_m*, of moat during Landward slope S_L = 1:3.

本研究的主要主题是介绍一种利用水垫降低溢流洪水能量的新对策。为此，进行了包括“LW”案例（带水垫的堤坝）和“OL”案例（仅堤坝）在内的实验室实验，以阐明水垫在堤坝溢流后水流结构变化中的作用，并降低能量. 护城河（深而宽的沟渠）具有不同的无量纲长度（L _m *  =  L _m / h _L；L _m是护城河的长度，其中h _L是堤坝高度）和深度（D _m *  =  D_米/小时_升；D _m是护城河深度）作为水垫提供在具有不同向陆坡度（ S _L）的堤坝的脚趾处。LW 和 OL 系统中的能量减少在较低溢流水深时非常接近，而 LW 系统中的能量减少比 OL 系统在较高溢流水深度时高 25%。大堤向陆坡度 ( S _L )、无量纲长度 ( L _m * ) 和深度 ( D _m * ) 的变化) 的护城河显着改变了流动结构，创造了六种不同的流动结构。然而，在 LW 情况下，通过改变 S L 、L m * 和 D m * 分别_观察到_1-6 % 、_1-3 %和1-5 _%的能量降低率差异。所有流动结构对能量降低的贡献都很大，但能量降低率在T-2流动结构中最大。命名为 T-2 和 T-6 的流动结构更可取，因为护城河内的水深增加，并且存在水下水力跃迁，这可以在向陆斜坡S _L  = 1:1、1:2 和通过减小L _m *时实现米_{_}* , 向陆坡S _L  = 1:3 期间的护城河。