### a. Preventative Water Control Measures

The occurrence of large scale floods leads to human and economic losses, greatly affecting socioeconomic activities and because the recovery and reconstruction requires a great amount of time and resources, preventative water control measures are important to keep disaster from occurring. For this reason, water control facilities such as levees, excavating river channels, dams, and discharge channels are developed systematically. Also, existing facilities are being maximized with dam renovation technology such as the redevelopment of existing dams as well as restructuring the capacity of several existing dams as part of measures to effectively utilize existing facilities. In addition, existing levees that are not sufficiently safe from permeative destruction or erosion due to floods are being strengthened.

Additionally, for “areas with a high likelihood of grave human casualties due to levee collapses in densely populated areas”, in coordination with town planning projects, a safe and pleasant living environment that protects the human lives of local

Figure II-7-2-2 International Comparison of Flood Control Safety

Country	River Name	Flood Control Safety Goals (Note) $ ^{1} $	Coverage (Note) $ ^{2} $
United States of America	Mississippi River Downstream	Around 1/500 (Note) $ ^{3} $	Approximately 94% (Note) $ ^{4} $
United Kingdom	Thames River	1/1,000 (Note) $ ^{5} $	100% (Note) $ ^{5} $
Netherlands	The coast including the center of the nation	1/10,000 (Note) $ ^{6} $	Around 94% (Note) $ ^{7} $
Japan	Arakawa River	1/200	Approx. 54%

(Notes) 1 Flood control safety goals: annual exceedance probability set as the development goal of the flood control facility

2 Development coverage: percentage of levees developed compared to the levees deemed necessary based on river improvement plans

3 "Sharing the Challenge: Floodplain Management into the 21st Century", Report of the Interagency Floodplain Management Review Committee to the Administration Floodplain Management Task Force, p.60, 1993.

4 "Report of the secretary of the army on civil works activities for FY 2008", Department of the Army

5 "Strategic Environmental Assessment Environmental Report Summary", Environment Agency, p.2, 2009.4.

6 "Flood Defence Act 1996" (http://www.safecoast.org/editor/databank/File/Flood%20Defence%20Act%201996.pdf)

7 “Water in Focus 2004 Annual report on water management in the Netherland”, Ministry of Transport, Public Works and Water Management in co-operation with the partners of the National Administrative Consultation on Water.

(http://www.rijkswaterstaat.nl/rws/riza/waterinbeeld/wib2004e/index.html)

Source) MLIT

residents will be formed and to increase the safety of areas away from rivers, the development of high-standard levees that do not collapse in the face of flooding that exceeds the planned capacity of facilities is being carried out.

### b. Preventing the Reoccurrence of Flood Disasters

In recent years, within regions that experienced flooding, river channels are excavated and levees are being built to improve the flow capacity of rivers, drainage pump stations are developed to prevent inside water flooding among other measures are being implemented intensively in a short time span to prevent or mitigate flooding.

### c. Flood Control Measures Tailored to River Basin Characteristics

For rivers that experience a significant decline in flood control safety due to river basin development or existing urban areas regularly subject to flood damages, it is important to ensure the water retention and flood dissipation functions of the river basin. Rivers such as these require the promotion of river basin measures and a variety of methods that taken into consideration regional characteristics to ensure safety and comfort.

## Column

## “Dam Regeneration” -Utilization through the Redevelopment of Existing Dams-

Dams fulfill their role in a variety of ways. From the viewpoint of effectively utilizing existing facilities, there is an increased demand for further utilizing existing dams and the Ministry of Land, Infrastructure, Transport and Tourism is promoting “dam regeneration”. Dam regeneration involves the enhancement of existing dams such as expanding the dam’s capacity, increasing discharge capacity, improving operations, sedimentation measures, and water quality measures in order to better utilize existing dams.

As one example of dam regeneration, the Tsuruta Dam redevelopment project is reaching the mature stage. This project is to strengthen the flood control functions of the existing Tsuruta Dam following the torrential rain disaster that occurred in the