|To develop a generalized method for the primary assessment of inter-levee floodplainpond environments in large Japanese lowland rivers, a generalized prediction modelfor freshwater mussel occurrence was built, and an application method for river managementwas suggested. Mussels were present in all of nine study rivers. Mussels occurred in73 of the 363 surveyed ponds, at 1 to 21 ponds in each river. The probability of mussel occurrencewas predicted using the relative height and area of each pond, with hump-shapedand positive relationships with mussel occurrence, respectively. As an example to demonstrateits application to river management, a floodplain assessment figure with a form similarto that of the discharge capacity figure, was created for the Kiso River.