Author(s)

CHEN-JIA HUANG & MING-HSI HSU

Abstract

Flooding often causes the devastating impact of people and the tremendous economy loss, especially in developed cities. Recently, many efforts have been made in urban flood modelling, which provides a useful tool for disaster mitigation. The high resolution flood modelling in large floodplain remains computationally demanding. Therefore, the multi-scale approach provided a rapid solution for solving the complex flow pattern in local region where densely distributed buildings often affect the propagation of overland flow, as well as excluding interior spaces from flooding.

An urban inundation model including the coarse and fine grid resolutions was developed to represent the blockage effect of buildings. The proposed model firstly solves the non-inertia overland flow equations using a coarse main grid for the global domain, then the results are used as the boundary conditions for the fine grid computation. The local refinement technique reflects the details of hydrodynamics in areas near buildings with high resolution. The computing of global domain and all the local regions of the multi-scale inundation model are able to improve the efficiency.

A synthetic case was adopted for model validation. The simulation results of multi-scale model demonstrated the good accuracy. The model was further applied to the simulation of typhoon Morakot event (2009), which induced the worst flooding that ever happened in Taiwan in half a century. The simulation results showed that the proposed model can reveal the better representation of water depth in local refined urban area and the computing efficiency was significantly improved for the real-time flood forecasting.

Keywords

blockage effect, Multi-scale, Urban inundation model