A Study on the Application of Cascade Type Flood Control to the Chikugo River

Review and analysis of vehicle stability models during floods and proposal for future improvements

“…Among the latter, some models establish a maximum limit for depth and flow velocity (DIPNR, ; Shand et al, ; Smith, Davey, & Cox, ) and others a maximum limit only for depth (Martínez‐Gomariz et al, ; Moore & Power, ). Finally, some authors have developed models that enable the calculation of vehicle stability either considering or disregarding its watertightness; that is, one of these models establishes the stability threshold by registering the combinations of flow velocity and depth that generate stability loss (Toda, Ishigaki, & Ozaki, ), another compares the forces acting on the vehicle (Oshikawa & Komatsu, ), and the third uses the Froude number and a mobility parameter (Arrighi et al, ).…”

“…Oshikawa and Komatsu () conducted experimental tests with 1:24 scale physical models of a Nissan March compact car and a 4WD Toyota Land Cruiser. From the results analysis, the stability threshold was determined as the ratio between the drag force and the friction one.…”

“…In the cases where water can enter the vehicle, there will be a decrease in the flotation force due to the vehicle porosity, which was defined with a minimum value of 0.0 when the vehicle was well closed and with a maximum value of 0.5 that corresponded to the cases where the dead weight of the vehicle and the buoyancy were balanced. Therefore, it is possible to define a safe zone below the obtained stability threshold with a friction coefficient of 0.4 and a porosity of 0.0, and a danger zone above the result for a friction coefficient of 0.6 and a porosity of 0.5 (Oshikawa & Komatsu, ) (Figure c).…”

“…Using a similar approach to that of Oshikawa and Komatsu (), Toda et al () performed laboratory tests using physical models at scale 1:10 of a sedan‐style vehicle and 1:18 of a minivan. These authors obtained friction coefficients equal to 0.26 for the sedan vehicle and 0.57 for the minivan with the car oriented in the flow direction and the handbrake on.…”

“…The analysis of Figure allows identifying how the studied stability models generate a wide range of stability thresholds, which are based on the decision criteria established in each case. For example, in the case of 4WD vehicles, with a flow velocity of 3.5 m/s, it can be observed that the stability models proposed by Shand et al () and Smith et al () consider it is not safe to drive with any depth, while the models proposed by Moore and Power (2002) and Martínez‐Gomariz et al () consider safe to drive with depths approximately equal to or less than 0.18 m and Oshikawa and Komatsu () establish this depth limit at approximately 0.45 m. Variations of similar order of magnitude are observed for large and small passenger vehicles.…”