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  7. PWRI and Fujitsu Develop Technology that Automatically Adjusts Parameters of Flood Forecasting Simulators

PWRI and Fujitsu Develop Technology that Automatically Adjusts Parameters of Flood Forecasting Simulators

Public Works Research Institute,Fujitsu Laboratories Ltd.

Tsukuba and Kawasaki, Japan, March 09, 2015

The Public Works Research Institute (PWRI) and Fujitsu Laboratories, Ltd., today announced that they have developed technology that automatically adjusts the parameters, such as the final infiltration rate and the runoff coefficient (ease by which rainwater enters soil and ease for water to flow downstream), of flood forecasting simulators that calculate a river's flow when predicting floods.

Currently, flood forecasting simulators are used in some river management work to predict the discharge of a river's flow, which is important in flood management measures. For a simulator to reflect the conditions of the river basin with high accuracy, it is desirable to use a distributed runoff model, which includes topography and models land-use distribution, such as forested and developed zones. However, determining the optimal parameters for increasing predictive accuracy has proved problematic.

Now PWRI and Fujitsu Laboratories have developed technology that automatically determines parameters for distributed runoff models based on the selection and application of optimization algorithms. As a result, flood forecasting simulators based on distributed runoff models can be operated configured to the optimal settings, and river managers can make appropriate decisions on measures for disaster prevention and mitigation based on the forecasted discharge of river flow.

Details of this technology will be announced by PWRI and Fujitsu Laboratories at the 59th Conference on Hydraulic Engineering of the Japan Society of Civil Engineers, opening Tuesday, March 10, at Waseda University in Tokyo.


River management offices already predict the river discharge during typhoons and heavy rains, and dispatch managers to affected areas to give residents evacuation orders and mitigate the effects in other ways. But with the increasing scale of natural disasters, such as concentrated downpours, a more sophisticated approach to flood defense is demanded.

Flood forecasting simulators are an effective way to predict river flows, which is an important part of flood defense. Distributed runoff models, which model the distribution of land use and topography near the river, enable detailed river simulations and sophisticated river management.

In order for distributed runoff models to be used more widely, Fujitsu Laboratories is working with PWRI from April 2014 to March of 2016 on a joint-research project for bringing mathematical optimization techniques to distributed runoff models(1).


For flood forecasting simulators based on the distributed runoff model to be broadly useful as a flood defense, the parameters used to model past floods need to be correctly tuned. This tuning process has required the advanced skills of specialists and expert knowledge on river engineering and hydrology.

About the Technology

As the product of their first year of collaborative research, PWRI and Fujitsu Laboratories have developed technology that automatically sets the parameters used in flood forecasting simulators (Figure 1).

Features of the technology are as follows:

1. Selects optimization algorithms for the distributed runoff model, tests against past floods

Taking rainfall data from past floods as inputs, the technology compares the discharge calculations produced by the flood forecasting simulator with actual discharge data. Here, the set parameters are automatically tuned with the calculation technique called mathematical optimization, which is a way to get the best possible answer from the applied rule in a small number of attempts.

Fujitsu Laboratories and PWRI evaluated 75 types of optimization algorithm and selected the 13 that best fit with the distributed runoff model. They also developed a mathematical optimization platform that automates the selection process.

For 15 examples of river floods in Japan, the partners compared actual discharge measurements with the calculation from the flood forecasting simulator. On the Nash-Sutcliffe model efficiency coefficient(2), which evaluates a model's predictive power, models are more accurate the closer their index value is to 1, and this model produced values of 0.9 and above (Figure 2), indicating accurate predictive power.

Figure 1: Mathematical optimization and calculating dischargeFigure 1: Mathematical optimization and calculating discharge

Figure 2: Actual and simulated dischargeFigure 2: Actual and simulated discharge

2. Analyzes relationship between flood characteristics and parameters

By analyzing the various statistics that can be used to characterize a flood and the parameters that have good reproducibility for each flood, the partners were able to clarify the relationship between a given parameter and a given discharge, for a ratio between rainfall and discharge volume. This knowledge is useful information when tuning parameters for a new flood.


With this technology, flood forecasting simulators based on the distributed runoff model can be run while parameters are tuned to optimal conditions, which will empower river managers to determine appropriate disaster prevention and mitigation measures based on river flows predicted under optimal conditions.

Future Plans

By performing validation using a variety of floods, PWRI and Fujitsu Laboratories seek to improve the predictive accuracy of this technology with the aim of practical implementation in fiscal 2016. Moreover, to make flood forecasting simulations more widespread, they will incorporate a mathematical optimization platform into the Integrated Flood Analysis System (IFAS)(3), evaluate its performance in multiple river basins, and work to achieve real-time flood forecasting by data assimilation through the integration of simulations and observational data.

  • [1] Research on the deployment of mathematical optimization methods in flood forecasting models

    Joint research for which PWRI publicly solicited partners, and for which Fujitsu Laboratories applied and was accepted. PWRI provided the flood forecasting simulation technology, as well as a simulator and data, and Fujitsu Laboratories provided mathematical optimization technology.

  • [2] Nash-Sutcliffe model efficiency coefficient

    A coefficient that assesses how well calculated values from a simulation model match observed measurements.
    Nash-Sutcliffe efficiency coefficient = 1 - (residual variance between predicted and observed values) / variance distribution of observed values

  • [3] Integrated Flood Analysis System (IFAS)

    An integrated analysis system for flood forecasting simulations developed and publicly released by PWRI:

About Public Works Research Institute

Public Works Research Institute accurately identifies social requirements, the people's needs and international needs and, by producing quality research results, aims to return benefits of its research results to society. In order to attain those achievements, the research departments of four institutions, Tsukuba Central Research Institute, Civil Engineering Research Institute for Cold Region, International Center for Water Hazard and Risk Management and Center for Advanced Engineering Structural Assessment and Research, implement research on prevention and reduction of natural disasters, improvement of living environment, advanced social capital stock management, measures regarding global environment issues such as energy/ resource saving, development of social capital suitable for the snow piling cold climate, advanced research and development such as new materials/ new construction methods for development of Hokkaido's agricultural and fisheries foundation and research and development in basic areas such as phenomenon/ mechanism analysis and general technologies that forms the foundation of the entire public works technologies.

About Fujitsu

Fujitsu is the leading Japanese information and communication technology (ICT) company offering a full range of technology products, solutions and services. Approximately 162,000 Fujitsu people support customers in more than 100 countries. We use our experience and the power of ICT to shape the future of society with our customers. Fujitsu Limited (TSE: 6702) reported consolidated revenues of 4.8 trillion yen (US$46 billion) for the fiscal year ended March 31, 2014. For more information, please see

About Fujitsu Laboratories

Founded in 1968 as a wholly owned subsidiary of Fujitsu Limited, Fujitsu Laboratories Ltd. is one of the premier research centers in the world. With a global network of laboratories in Japan, China, the United States and Europe, the organization conducts a wide range of basic and applied research in the areas of Next-generation Services, Computer Servers, Networks, Electronic Devices and Advanced Materials. For more information, please see:

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Date: 09 March, 2015
City: Tsukuba and Kawasaki, Japan
Company: Public Works Research Institute / Fujitsu Laboratories Ltd.