One of the prominent features in the Agusan River basin is the presence of the Agusan Marsh covering a total area of 19,197 hectares (47,440 acres). The marsh serves a flood retention basin for the Agusan River, cutting the high discharge of water causing flash floods in the lower reaches of the river. Aside from that, the marsh harbors unique and pristine habitats like the sago and peat swamps forest and is a home to endangered and endemic flora and fauna.