Abstract
Frequent flash floods in recent years have resulted in a major impact on the living environment, urban planning, economic system and flood control facilities of residents around the world; therefore, the establishment of disaster management and flood warning systems is an urgent task, required for government units to propose flood mitigation measures. To conserve the numerical accuracy and maintain stability for explicit scheme, the Courant–Friedrich–Lewy (CFL) condition is necessarily enforced, and it is conducted to regulate the relation between the numerical marching speed and wave celerity. On the other hand, to avoid the problem of flow reflux between adjacent grids in executing 2D floodplain simulation, another restriction on time intervals, known as the Hunter condition, was devised in an earlier study. The objective of this study was to analyze the spatial and temporal distribution of these two time-interval restrictions during runoff simulations. Via a case study of the Komarovsky River Basin in Russia, the results show that at the beginning of a storm, the computational time interval is restricted by the CFL condition along the upstream steep hillsides, and the time interval is subject to the Hunter condition in the mainstream during the occurrence of the main storm. The reason of a reduction in computational efficiency, which is a common problem in conducting distributed routing, was clearly explained. To relax the time-interval restrictions for efficient flood forecasting, the research findings also indicate the importance of integrating modified hydrological models proposed in recent studies.
Highlights
IntroductionOwing to the complete development of digital topography treatment [1,2,3], the grid-based digital elevation model (DEM) datasets have been applied to a variety of study fields
Typhoons or torrential rains have become more frequent in recent years, more careful and thorough consideration for establishing flood warning system is needed to alleviate flood disasters.Owing to the complete development of digital topography treatment [1,2,3], the grid-based digital elevation model (DEM) datasets have been applied to a variety of study fields
“Integrated” denotes the algorithm that integrates both the quasi-2D MacCormack recursive formulation and the Bates inertial momentum formulation into the conventional explicit scheme; the computational time step ∆t can be lengthened to 60 s without being subject to the CFL condition and Hunter condition
Summary
Owing to the complete development of digital topography treatment [1,2,3], the grid-based digital elevation model (DEM) datasets have been applied to a variety of study fields. Several studies have shown that the simplified non-inertia wave equation can still provide appropriate solutions within tolerable errors in overland-flow simulations even for a rugged landform [6,9]. In comparison to the fully 2D model, quasi-2D models may neglect some significant aspects of the spatial variability of hydraulics and are too simplistic in the treatment of flow paths; owing to recent developments in topographic measurement for high resolution data, many previous studies have noted a growing prospect for quasi-2D models applied to the floodplain simulation [10,11,12]
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