2021 Volume 86 Issue 788 Pages 2431-2440
In this study, the authors conducted research of the repairing cases of flooded detached houses, aiming to clarify the relationship between flood damage and repairing method that were carried out subsequently of flooded houses.
The authors made technical interviews with a regional building contractor who repaired flooded detached houses in Mihara City, Hiroshima Pref., which is one of the areas affected by the heavy rains in July 2018 (Heavy rains of July Heisei 30). They conducted a case study of 11 selected houses and examined what repairing work were performed focusing on whether replacement or continuous use of each building part of the houses was selected. The results indicate that there is little difference of repairing work between construction types of house and that repairing methods are likely to be characterized by flood level.
With collected data of construction cost of the cases, the authors conducted quantitative analysis between direct construction cost and degree of flood damage. As a result of a linear regression analysis, a simple regression model using flood volume (m3) as an explanatory variable, which is the product of repaired floor area (m2) and flood level (m) above floor, was evaluated as intuitively easy to comprehend and with high compatibility.
The authors considered simulated repairing method of a standard model house at different four flood levels to verify differences of repairing method and construction cost fluctuation depending on height of flood levels. The elevation from underfloor to 0.2m height above floor was found to have the most impact on the overall increase in construction cost from underfloor to 2.0m height above floor, because sanitary equipment, floors, internal fittings and furnitecture are to be replaced at the same time. The elevation from 0.9m to 2.0m above floor, the cost increase due to the renewal of windows, front doors and staircase are particularly large. These construction works that occur collectively when a flood level exceeds a certain height would contribute to the discrete increase in cost. In contrast, the range of the internal wall to be replaced enlarges as the flood level gets higher. Therefore, the cost from 0.2m to 0.9m above floor increases continuously.
Comparing the predicted values and the estimated values of the model house, the predicted ones are particularly larger at 2.0m above floor although it was roughly fitted in the range of 0.2m to 0.9m. Such differences are considered caused by discrete increases in cost described above and the sample data including additional cost. Further studies are needed in the future to refine the predict model.
The obtained findings indicate the repair methods performed subsequently of flooded detached houses are likely common depending on the flood level. The normal repairing methods presented in this study can be used as a basic plan for residents and construction contractors to consider repairing methods. It is expected to be used as a starting point for clearly discussing what repairing method will be optimal according to their budget situations and future living style.
