This investigation was the last of a 4 phase study of the sediment regime of the Mississippi River Basin. Phase III dealt with suspended-sediment sampling, analysis, and load-computation procedures used at key stations on major streams in the Mississippi River Basin and the possible correlation of these procedures with the downward trend in suspended-sediment loads. In this Phase IV study, existing regime equations were examined in light of their applicability to major alluvial river systems. The principal focus of the Phase IV study was the examination of the effects of changes in suspended-sediment loads as they relate to the regime of alluvial rivers.