Physical Description

Mobile Bay drains the fourth largest watershed in the United States in terms of flow volume, and is the receiving basin for the sixth largest river system in the United States. 65% of Alabama’s land area drains its waters into Mobile Bay. (Mobile Bay NEP)

Mobile Bay is Alabama’s only port for oceangoing ships. The Bay is also a point of entry for hundreds of cruising vessels (or pleasure cruisers) who travel the 450 mile trip all the way to the Tennessee River.

In 1999, the Port of Mobile was the 14th largest port in the nation in total tonnage, ahead of other well known ports such as Tampa, Seattle, Charleston and Savannah. (AL State Docks)

Mobile Bay is Alabama’s central estuary system. In simplest terms, an estuary is defined as an area where rivers meet the sea. They are transitional zones where freshwater rivers meet tidally influenced marine waters. Estuaries are considered environmentally and economically important because of their exceptional biological diversity and productivity. (Mobile Bay NEP)

Where the Mobile River meets the Mobile Bay is more accurately described as a delta than as a river. Most of the land area between the Mobile River on the western edge of the delta and the Tensaw River on the eastern edge is marshlands. About a third of the area is a vast network of waterways. More than 250 separate waterways (rivers, bays, creeks, bayous, lakes, cutoffs, branches, and sloughs) are charted and identified by the US Geological Survey. (Rivers of Alabama)

Mobile bay

Mobile Bay is approximately 32 miles tall, 23 miles wide at its widest point, and 10 miles wide at the city of Mobile. Mobile Bay’s average depth is only about 10 feet, which is among the most shallow for a bay this size. (Mobile Bay NEP)

At 62,000 cubic feet per second, on average, the Mobile Bay estuary has the fourth largest freshwater flow in the continental United States.

At 43,662 square miles, the Mobile Bay watershed is the sixth largest watershed basin in the United States. (Mobile Bay NEP)

An estimated 4.85 million metric tons of sediment enter the estuary annually, with 33% being deposited in the Delta, 52% in the Bay and the remainder flowing through to the Gulf of Mexico. (Mobile Bay NEP)


Rainfall in the bay area averages 65 inches, the highest average for a city the size of Mobile in the US.

The Coastline has one of the highest frequencies of hurricane landfalls in the nation. Average tidal changes average less than 1.5 feet, with maximum tidal changes of 2.5 feet.