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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 8 | Copyright
Nat. Hazards Earth Syst. Sci., 16, 1821-1839, 2016
https://doi.org/10.5194/nhess-16-1821-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 09 Aug 2016

Research article | 09 Aug 2016

Ensemble flood simulation for a small dam catchment in Japan using 10 and 2 km resolution nonhydrostatic model rainfalls

Kenichiro Kobayashi1, Shigenori Otsuka2, Apip3, and Kazuo Saito4 Kenichiro Kobayashi et al.
  • 1Research Center for Urban Safety and Security, Kobe University, 1-1 Rokkodai-machi, Nada-ku, Kobe, 657-8501, Japan
  • 2RIKEN Advanced Institute for Computational Science, Kobe, Japan
  • 3Research Centre for Limnology, Indonesian Institute of Sciences (LIPI), Bogor, Indonesia
  • 4Meteorological Research Institute, Tsukuba, Japan

Abstract. This paper presents a study on short-term ensemble flood forecasting specifically for small dam catchments in Japan. Numerical ensemble simulations of rainfall from the Japan Meteorological Agency nonhydrostatic model (JMA-NHM) are used as the input data to a rainfall–runoff model for predicting river discharge into a dam. The ensemble weather simulations use a conventional 10km and a high-resolution 2km spatial resolutions. A distributed rainfall–runoff model is constructed for the Kasahori dam catchment (approx. 70km2) and applied with the ensemble rainfalls. The results show that the hourly maximum and cumulative catchment-average rainfalls of the 2km resolution JMA-NHM ensemble simulation are more appropriate than the 10km resolution rainfalls. All the simulated inflows based on the 2 and 10km rainfalls become larger than the flood discharge of 140m3s−1, a threshold value for flood control. The inflows with the 10km resolution ensemble rainfall are all considerably smaller than the observations, while at least one simulated discharge out of 11 ensemble members with the 2km resolution rainfalls reproduces the first peak of the inflow at the Kasahori dam with similar amplitude to observations, although there are spatiotemporal lags between simulation and observation. To take positional lags into account of the ensemble discharge simulation, the rainfall distribution in each ensemble member is shifted so that the catchment-averaged cumulative rainfall of the Kasahori dam maximizes. The runoff simulation with the position-shifted rainfalls shows much better results than the original ensemble discharge simulations.

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This paper presents a study on short-term ensemble flood forecasting for small dam catchments in Japan. Numerical ensemble simulations of rainfall from the Japan Meteorological Agency nonhydrostatic model are used as the input data to a rainfall–runoff model for predicting river discharge into a dam. Overall results are considered on some level helpful for decision-making related to flood control, especially as a supporting tool in addition to discharge observations and radar rainfalls.
This paper presents a study on short-term ensemble flood forecasting for small dam catchments in...
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