The Yodo River was prone to frequent large-scale floods, causing great damage to the people living in the river basin, so the Meiji government began major renovation work on the Yodo River in 1896. A lock gate (completed in 1907) and a wash weir (completed in 1910) were installed at Kema, which regulated the amount of water flowing into the old Yodo River (Okawa) and made shipping easier. Both are made of brick, with granite in key areas. The current lock gate and wash weir were newly built in 1974, but the old Meiji-era No. 1 lock gate and wash weir are preserved within Yodo River Park and are designated as Important Cultural Properties of Japan.