Immediately west of Perdido Pass, for about one mile, the beaches have widened significantly since 1970. This has happened because of the engineering at the pass. The western Perdido Pass jetty, built in 1968-69, is a high, rock jetty designed to keep sand from moving back east into the pass. Much of the sand dredged from Perdido Pass has been placed immediately to the west of the jetty during the past 20 years. This has combined with the natural trapping of sand against the jetty to widen these beaches.
The sand trapped around Perdido Pass in the areas shown above has
caused beach erosion in western Orange Beach.
The trapping of sand adjacent to the western jetty is called a “fillet” by analogy with a fillet weld in the corner of two pieces of metal. The sand fillet formed as the beach planform (shape of the beach as viewed from above) moved toward a new equilibrium position adjacent to the jetty. When waves are approaching the Alabama coast from the southwest and the longshore sand transport is to the east, sand is free to move off the beaches of western Orange Beach into this area. However, when waves are approaching the Alabama coast from the southeast and the longshore sand transport is to the west, the sand in this area is partially sheltered by both the rock jetty itself and the shoals around the mouth of Perdido Pass. Essentially, this sand is partially, permanently trapped here. Some sand has also been placed in upland, not beach, sites around the pass. And some sand has been trapped in a new ebb-tidal shoal out beyond the mouth of the jetties. The total trapping of former beach sands by engineering at Perdido Pass since 1968 is over 3 million cubic yards.
Sand has been indirectly mined from the beach system at Perdido Pass for decades.
This sand came off the Perdido Key beaches, was dredged out of the pass
and placed here, and then, many years later, trucked away.
The main problem is that all this trapping has caused erosion of the beaches for miles to the west. This includes the beaches of western Orange Beach (more than 1 mile west of the pass) and the beaches of Gulf Shores. There are also some problems on the Alabama Point beaches because there is too much sand. These problems are standing water on an unnaturally wide beach, unnaturally high scarps (vertical cliffs) on the beach face that are unsafe for humans and prevent successful sea turtle nesting, and complaints from tourists about the very long walk to the beach. This report recommends that all the clean sand dredged from Perdido Pass in the future be placed on the beaches over 1˝ miles to the west of the jetties.