 The Missouri 's nickname , the " Big <unk> " , was inspired by its enormous loads of sediment or silt – some of the largest of any North American river . In its pre @-@ development state , the river transported some 175 to 320 million short tons ( 159 to 290 Mt ) per year . The construction of dams and levees has drastically reduced this to 20 to 25 million short tons ( 18 to 23 Mt ) in the present day . Much of this sediment is derived from the river 's floodplain , also called the <unk> belt ; every time the river changed course , it would <unk> tons of soil and rocks from its banks . However , <unk> and channeling the river has kept it from reaching its natural sediment sources along most of its course . <unk> along the Missouri trap roughly 36 @.@ 4 million short tons ( 33 @.@ 0 Mt ) of sediment each year . Despite this , the river still transports more than half the total silt that empties into the Gulf of Mexico ; the Mississippi River Delta , formed by sediment deposits at the mouth of the Mississippi , constitutes a majority of sediments carried by the Missouri . 
