勝田川

Gazing at the Katsura River, also known as the Katsura-gawa, have you ever wondered about its journey? The Katsura River, or Katsutagawa as it’s sometimes called, meanders through the heart of Chiba Prefecture. It’s a tributary of the Tone River, ultimately flowing into Tokyo Bay. The Katsura River begins its journey in eastern Chiba City, near the border of Wakaba and Koizumi districts. It flows north, crossing between Chiba City and Yotsukaido City. The river then continues, passing the border between Hanamigawa Ward and Yotsukaido. Here, it merges with a drainage canal from Ohigashi-kata. Further along, near Sakuranomiya Bridge, the Katsutagawa joins the Unarizuka Drainage Canal. On the left bank sits the Miharashino New Town, home to the Miharashino regulating pond, built for residential development. Nearing the border of Yachiyo City and Hanamigawa Ward, the Katsura River converges with another drainage canal from the Koteshi-dai area. A bit further downstream, near Katsutadai-Minami, it finally merges with the Inba Drainage Canal (also known as the Hanamigawa River) and continues to Tokyo Bay. The river’s course hasn’t always been this way. Originally, the Katsura River flowed directly into the Inba Marsh. With the completion of the Inba Drainage Canal, the river’s mouth shifted, connecting it to the Hanamigawa and then Tokyo Bay. The Katsura River’s history is intertwined with flood control efforts. Starting in the 1970s, residential development in the river basin increased, leading to frequent flood damage during typhoons and heavy rains. In 1990, the Katsura River was designated for improvement. River modification projects commenced, aiming to mitigate flood risks. These projects, including bank protection works, dredging, and bridge replacements, were a joint effort between Chiba City, Yotsukaido City, Saku City, and Yachiyo City, all part of the Katsura River Improvement Council. The extensive work required significant time and resources. A temporary pump drainage facility was installed in Koizumi Town in 2007. By 2008, modifications were complete up to 1.5 km from the confluence with the Third Drainage Canal near Midorigaoka. Full completion was initially projected for 2015, but due to Chiba City’s financial challenges, the timeline has been delayed. Even amidst these large-scale projects, local initiatives have blossomed. The Koteshi-dai Regulating Pond, initially built for water storage, became a haven for biodiversity thanks to its rich natural surroundings. In 2004, a collaborative research project between Chiba City and Chiba University transformed the pond into a multi-natural type regulating pond. Involving local schools and municipalities, this project created a beloved space for the community. Similarly, the Unarizuka Regulating Pond, completed in 2008, now offers a water storage capacity of 53,000 cubic meters, with plans for expansion. The Katsura River continues to evolve, shaped by both large-scale infrastructure projects and community-driven environmental initiatives.