For lowland areas in eastern Tokyo, which have repeatedly suffered from storm surges and flooding, the Bureau’s river improvement efforts focus on installing embankments to protect against storm surges and other hazards, as well as making river control structures more resilient against earthquakes and water intrusion. In implementing those measures, the Bureau also works to create waterfront areas that attract people and provide a bustling atmosphere, by such means as building multiple esplanades that are linked to each other.
Protecting River Control Structures against Earthquake and Tsunami
Following the Great East Japan Earthquake of March 2011, the TMG compiled in December 2012 a plan for improving river control facilities in lowland areas of eastern Tokyo to protect them against floods from earthquakes/tsunami, with the aim of maintaining the functions of each facility and preventing inundation from tsunami, etc. even in the event of the biggest earthquake predicted.
The plan states that the TMG will take measures by fiscal 2021 to improve the seismic and/or water resistance of target facilities, which are embankments with a total length of about 86 km and 22 facilities including floodgates and pumping stations. It also says that works on the 22 facilities and embankments that are not protected by floodgates, which urgently need to be fortified, should be completed by 2020 (fiscal 2019).
Improvement of Storm Surge Control Structures
With the aim of protecting eastern Tokyo’s lowland areas from storm surges as big as those wrought by the 1959 Ise-wan Typhoon, the TMG is installing embankments and other structures in those areas, most of which are located east of the Sumidagawa River. Work has been almost completed on the Sumidagawa and other major rivers, and the construction is still underway in areas including Myokenjima Island in the Kyu-Edogawa River.
In normal times
During storm surge
When Typhoon No. 15 (Typhoon Roke) hit Tokyo in September 2011, a storm surge increased the level of the Sumidagawa River, to the extent shown in these pictures of the left bank upstream of the Shin-Ohashi Bridge.
Installing Super Levees and Gently Sloping Embankments
On the Sumidagawa and other major rivers, super levees and gently sloping embankments are being constructed to make the areas better protected against a potential strong earthquake and to improve the riverside environment. Construction is carried out in an integrated manner with redevelopment and other community development projects in areas along the rivers. Also, terraces are built before the completion of levees/embankments to allow the public to enjoy jogging and strolling in waterfront areas.
Projects on Koto Inner Rivers
In the Koto Delta, an area at particularly low altitudes surrounded by the Arakawa and Sumidagawa rivers, the Bureau carries out projects on inner rivers to protect the area from flooding caused by embankment failure due to earthquake. For rivers in the western part of the area, earthquake-proof embankments are being built. For rivers in the eastern part, where efforts are made to keep the normal water levels low, river channel improvements are being implemented with attention paid to the river environment.
Creating Vibrancy in Waterfront Areas
Building continuous terraces and other various efforts are underway to create waterfront areas that attract people and provide a bustling atmosphere and to enhance the attractiveness of Tokyo, which was once called the “City of Water.” To make waterfront areas a place where many people always visit, the Bureau takes further measures to increase their charm, based on the Concepts for Waterfront Area Development on the Sumidagawa and Other Rivers formulated in fiscal 2013.