Impact of floating debris on houses during floods and vegetation-based mitigation

Debris generated by the destruction of houses in a floodplain can cause damage to structures in the way of floodwaters due to the impact of different hydraulic forces. In this study, the impacts of different hydraulic forces, including impact force, hydrostatic force, hydrodynamic force, fluid force index (FFI) and moment index (MI), on house models of different porosity were examined. The impacts of these hydraulic forces on house models for different types of debris (rectangular and cylindrical debris) were also investigated. The results showed that type D5 cylindrical debris (with the greatest mass) had a greater specific gravity (0.206) than the other types of debris examined, which was why it resulted in a higher magnitude of impact force (40%) for the double porous house model (DPHM). Type D3 cylindrical debris (with the longest length) produced the highest value of hydrostatic force (40%). A higher velocity of flow caused a greater magnitude of the FFI (60%) on the impermeable house model (IHM), and this reduced with an increase in the porosity of the house model. The highest MI (97%) acted on the IHM because of greater flow velocity and water depth on the upstream side. Under different types of debris, vegetation provided as a countermeasure on the upstream side of the house model reduced the impact force by 10–22% for the DPHM and by 1–12% for the SPHM; the hydrostatic force was reduced by 12–59%. Hydrodynamic force reduction was observed to be 30% when vegetation was provided on the upstream side of house models of different porosity. Providing vegetation as a countermeasure reduced the FFI and MI by up to, respectively, 70% and 63.39% for the IHM.