Abstract
Clarifying hydrologic behavior, especially behavior related to extreme events such as flash floods, is vital for flood mitigation and management. However, discharge and rainfall measurement data are scarce, which is a major obstacle to flood mitigation. This study: (i) simulated flash floods on a regional scale using three types of rainfall forcing implemented in a land surface model; and (ii) evaluated and compared simulated flash floods with the observed discharge. The three types of rainfall forcing were those observed by the Automated Meteorological Data Acquisition System (AMeDAS) (Simulation I), the observed rainfall from the Ministry of Land, Infrastructure and Transportation (MLIT) (Simulation II), and the estimated rainfall from the Multi-purpose Transport Satellite (MTSAT), which was downscaled by AMeDAS rainfall (Simulation III). MLIT rainfall observations have a denser station network over the Ishikari River basin (spacing of approximately 10 km) compared with AMeDAS (spacing of approximately 20 km), so they are expected to capture the rainfall spatial distribution more accurately. A land surface model, the Minimal Advance Treatments of Surface Interaction and Runoff (MATSIRO), was implemented for the flash flood simulation. The river flow simulations were run over the Ishikari river basin at a 1-km grid resolution and a 1-h temporal resolution during August 2010. The statistical performance of the river flow simulations during a flash flood event on 23 and 24 August 2010 demonstrated that Simulation I was reasonable compared with Simulation III. The findings also suggest that the advantages of the MTSAT-based estimated rainfall (i.e., good spatial distribution) can be coupled with the benefit of direct AMeDAS observations (i.e., representation of the true rainfall).
Highlights
Clarifying the hydrological behavior of a catchment area, especially behavior related to extreme events such as flash floods, is vital for flood mitigation and management
The performance of the downscaled Multi-purpose Transport Satellite (MTSAT) and Automated Meteorological Data Acquisition System (AMeDAS) rainfall observations was demonstrated by comparison with the MLIT rainfall observations
Because MLIT data were characterized by a denser station network over the Ishikari River basin compared with AMeDAS, it is likely more accurate than the other rainfall measurements, and likely represents the spatial distribution of rainfall more accurately
Summary
Clarifying the hydrological behavior of a catchment area, especially behavior related to extreme events such as flash floods, is vital for flood mitigation and management. Some studies have focused on flash flood mitigation, including risk estimation [1], early detection [2], and severity [3,4]. The magnitude of peak discharge and time to peak discharge during flash flood events are important parameters that should be assessed to help mitigate their disastrous effect. This information is usually derived by analyzing discharge measurements. Problems arise when the catchment is ungauged because the gauges are damaged by hazards. Rainfall-runoff models are used to simulate discharge as an alternative way to obtain hydrologic data
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