Key institutions in Japan’s hydromet landscape have evolved since the 1950’s. For example, hydrological institutions have undergone several changes, such as after the enactment of the 1964 River Law Act (revised version). This law required authorities tasked with managing rivers to adhere to integrated river basin management principles, as opposed to more area-focused disaster management practices that were prevalent prior to this (e.g., shifting from circle levees, which only protect the builder’s community, to continuous levees, which ensure more equitable protection for the wider population). As for meteorological services, the regulatory framework was established under the Meteorological Service Act of 1952, which designated the Japan Meteorological Agency (JMA) as the authoritative body responsible for issuing emergency warnings.
In terms of legal framework, Japan’s laws assign clear roles and responsibilities for the National Hydrological Service (WDMB/MLIT), the National Meteorological Service (JMA), and other key stakeholders to ensure effective coordination.