～Making the river both disaster resistant and profitable～

The Arakawa exists in a capital region which functions as a center of population and assets, as well as of social and economic activities. For the dikes of such a river to break, the result would be catastrophic damage.
To prevent such damage, we promote the maintenance of a super levee as an essential measure. Additionally, we implement many kinds of approaches such as weak point resolution for water control and a measure for water control integrated with the river basin.

1. Super Levees
2. Reconstruction of Bridges that interfere with Flood Control Measures
3. Integrated Flood Control Measures of Shingashi Rive

A Super Levee in the Komatsugawa District

• A super levee is about 30 time as wide(about 200m to 300m)as it is high, so that even if it is overtopped, the flowing water does not breach the levee because it flows slowly across its top surface.
• A super levee is built on land designated as a special high standard levee district subject to relaxed restrictions to permit normal use of the land.
• So super levee projects are implemented in conjunction with urban redevelopment, land rezoning projects or other urban planning.
• Super levees have been completed or are under construction on approximately 15% of the total length of the levees in the jurisdiction (about 60 kilometers on both side of the river).

A new neighborhood is created as home construction begins. （Edogwa ward）	The top of super levee in the Kita-Akabane District is used as a river disaster protection station.（Kita ward）	In the Kawaguchi District, a new school is built on the super levee.
Before improvement, a row of factories along the levee.（Adachi Ward）	A new neighborhood is created by an integrated urban residential land improvement support projectt（Adachi Ward）

• The girders of some of these bridges are lower than nearby levees, interfering with flood control.
• Construction of related revetments was completed in 2002.
• Design work to prepare for the reconstruction of the Arakawa Bridge started in 2004.

Reconstruction of Bridges that interfere with Flood Control Measures	New bridge on the Keisei Oshiage Line that is 4.1m higher than the old bridge.
Arakawa Bridge on the Keisei Narita Line with girders that are about 4m lower than the upstream and downstream levees.	Arakawa Bridge with Girders Lower than the Height of Surrounding Levees

• Integrated Flood Control Measures are being taken in the Shingashi RiverBasin.
• River basin measures divide the river basin into a water retention district and a water retarding district and include measures suited to the characteristics of each.

During Rainfall
water seeps underground, limiting the　discharge into rivers to prevent floods from inundation the land.

Before Urban Development Most rainwater seeps underground or is stored in paddy fields or ponds, restricting the quantity that flows into rivers.

After Uban Development The ground is covered by concrete, and ponds and forests have disappeared, increasing the discharge into rivers and inundating low land along the river course..

Integrated Flood Control Measures

Regulating pond and infiltration wells constructed on the corner of a building lot.

A rainwater infiltration inlet that allows rainwater falling on a roof to seep underground.