The Katase River refers to the approximately 3-kilometer-long segment of the river from the city of Fujisawa (藤沢), where the Sakai (境川) and Kashio (柏尾川) rivers join, to the point at Enoshima Island, where the Katase River flows into Sagami Bay. The river's name comes from the Katase complex of hills (片瀬山) along which the river flows.
The Katase River and its tributaries are prone to flooding, especially in spring and the typhoon season in late summer and early autumn. Consequently, they were encased in concrete in the postwar period. Nowadays, they still flood, but don't overflow their banks as often as in the past.