“Did you hear the one about the river that became a city planner?” No? Then you are in the right place here at the Tsurumi River. It’s quite a tale.
The Tsurumi River begins its journey in Kamioyamada-machi, Machida, Tokyo. From there, it meanders for 42.5 kilometers. It finally empties into Tokyo Bay at Yokohama.
But the Tsurumi River’s story isn’t just about its physical journey. It’s about how it shaped the lives of nearly two million people. Its basin is home to them. Rapid urbanization dramatically changed the landscape. By the late 2000s, urban areas covered over 84% of the Tsurumi River basin. This is compared to only 10% in 1958.
This rapid growth brought challenges. Controlling floods became a major concern. In response, a special committee was formed. It included experts from academia, local municipalities, and river administrators. They worked together to find solutions.
Their goal was to balance river development with flood control. They came up with integrated measures. These measures addressed urban rain runoff during city planning. This initiative became a model for integrated flood control in Japan.
But urbanization continued and new problems arose. Environmental issues, disaster prevention and ongoing flood control were a constant concern. It became necessary to revitalize the river. A “Sound Water Cycle” concept was developed. The aim was to restore the relationship between people and the Tsurumi River.
This required cooperation. Cooperation between administrative sectors, citizens, businesses, and NGOs was key. The Tsurumi River Basin Commission invited public participation. Over a hundred residents registered. They contributed to the planning process.
Implementing the Tsurumi River Basin Water Master Plan took six years. Short-term targets were set. Progress was continuously reviewed. Measurable indicators were used to monitor progress.
The Tsurumi River has faced serious floods. In September 1982, a typhoon caused extensive damage. The average two-day rainfall in the basin was 218 mm. The water level at Sueyoshi Bridge reached 4.02 meters. The peak flow rate was 1,051 cubic meters per second. Many buildings experienced flooding.
Efforts to acquire land for flood control began in 1985. In 1989, the Tsurumi River New River Basin Improvement Plan was created. It set the basic high water flow rate at Sueyoshi Bridge at 1,300 cubic meters per second. The planned high water flow rate was set at 1,050 cubic meters per second.
A multipurpose retarding basin project was launched. It is a major part of the river improvement project. The goal is to create communities that are highly resistant to flood damage.
The Tsurumi River Multipurpose Retarding Basin is located in Kozukue-cho and Toriyama-cho. It covers 84 hectares. Its total water storage capacity is 3,900,000 cubic meters.
So, next time you cross the Tsurumi River, remember its journey. Remember how it transformed from a simple river into a central figure for the area. It is still vital for the safety and well-being of nearly two million people.