Refers to a shallow part of a river or a river shallow enough to cross. In modern everyday Japanese, 浅瀬 is usually the more transparent word; 高瀬 can sound literary, regional, or place-name-like.
Abbreviation of 高瀬舟, a shallow-draft river boat or flatboat. This use is limited and often has a historical or transport-related feel rather than being an ordinary modern word for boat.