The river is a " consequent stream " or a " tidal river " , which means that the Vermilion was formed from the bottom up . The river was created by Vermilion Bay : tides and other natural actions in the bay slowly eroded the marshes and other features of the landscape as the river crept northward . This process brought the channel that would one day become the Vermilion River as far north as Lafayette , Louisiana . Much later a distributary of Bayou Teche made its way south and eventually linked up with the consequent stream , forming a true north-south flowing river . During times of heavy-rain events , parts of the Vermilion will experience negative discharge , reversing direction and flowing north . At the Surrey Street stream gauge in Lafayette , Louisiana , maximum historic positive discharge was 6,280 ft ³ / s on July 17 , 1989 . Maximum negative discharge , -11,300 ft ³ / s , occurred on August 13 , 2016 during the 2016 Louisiana floods . The reverse-flow phenomenon occurs because the watershed areas in the city of Lafayette are highly developed . Rainfall runoff from this urban area enters the Vermilion River with larger volumes and at a faster rate than runoff upstream . This raises the water level in the Vermilion River along the southern areas of Lafayette . This rise in water levels sometimes exceeds the water level in reaches upstream of Lafayette , thus causing the reverse-flow effect . Also , when water levels in the Vermilion River exceed certain stages , water begins to enter the Bayou Tortue Swamp Area . This swamp has a great capacity to hold water , which also contributes to the reverse flow effect . The water from the Vermilion River enters Bayou Tortue Swamp through two coulees . Coulee Crow and Bayou Tortue are located upstream of the Surrey Street bridge on the Vermilion River
2016 Louisiana floods
2016 Louisiana floods
Vermilion River (Louisiana)