2005 Pre Katrina Racoon Island Survey

2005 Prehurricane Survey of Raccoon Island, Louisiana

By:

Thomas C. Michot (Pilot/Biologist), USGS - NWRC
Chris Wells (Observer/Geographer), USGS - NWRC

Flight Date:	August 27, 2005
Aircraft:	N727 (DOI 08), Cessna 185 Amphibian
Route of flight:	Lafayette, Bay Junop, Raccoon Island, Bay Junop, Old Oyster Bayou, Lafayette
Storm Name:	Hurricane Katrina
Storm Date (projected landfall):	August 29, 2005
Max sustained winds (projected):	Category 5

Background
Raccoon Island is Louisiana’s most important seabird nesting site west of Breton Sound. Numerous seabird species including the brown pelican (Pelecanus occidentalis), black skimmer (Rynchops niger), sandwich tern (Sterna sandvicensis), laughing gull (Larus atricilla) nest on the island and forage in the important fishery areas west of the island.

The low tide extent of the island has declined since the 1950s from nearly 283 ha (700 acres) to 97 ha (240 acres) mapped in 2003. The most dramatic losses have been noted in the wake of major storms such as Hurricanes Audrey (1957), Betsy (1965), Carmen (1974), and Andrew (1992). To protect this important barrier island rookery from further loss, State and Federal partners built an experimental system of breakwaters in hopes of lessening the erosion of the island. Hurricane Lili’s impact on the island in 2002 appeared to have proved the concept that the breakwaters help. It is more than likely that Hurricane Katrina will provide an additional, if unwelcome test of the breakwater protection.

Researchers at the USGS National Wetlands Research Center along with other Federal and State agencies have been monitoring Raccoon Island for decades resulting in a series of vegetation habitat maps dating back to the 1950s and breeding bird colony data since the 1980s. Most of the nesting by the seabirds takes place on the vegetated, eastern portion of the island, about half of which is protected by the breakwaters. This information has been used to guide management of this important resource for the benefit of the species and for Nation.

Methods
Observations were recorded and oblique digital photographs were taken from the aircraft of the island at two altitudes, 350 m (1,148 ft) and 180 m (591 ft). The island was circled at both altitudes with overlapping photographs acquired along both shorelines over the length of the island. In addition, several photographs of the eastern end of the island were taken at a near vertical angle to provide more details for photointerpretation and mapping.

Photographs

Oyster Bayou. This is a long-term marsh study site for USGS research scientists.

Raccoon Island, 350-m altitude. Western end of island viewed from the north.

Raccoon Island, 350-m altitude. Middle portion of island. Vegetated but not protected by breakwaters.

Raccoon Island, 350-m altitude. Eastern portion of island. Vegetated and protected by breakwaters.

Raccoon Island, 350-m altitude. View of entire island from the east. Easternmost breakwaters are clearly visible.

Raccoon Island, 350-m altitude. Easternmost end of island viewed from south. Breakwaters and mangroves are clearly visible. Also note the well developed tombolos (sand accretion) attaching the breakwaters. Some vegetative colonization is occurring on the tombolos.

Raccoon Island, 350-m altitude. Near-vertical photographs of the eastern end of the island behind the breakwaters. Vegetation patterns are evident.

Raccoon Island, 350-m altitude. Central and western end of the island from the south.

Raccoon Island, descending to 180-m altitude. View of entire island from the west.

Raccoon Island, 180-m altitude. Western end of island. Mostly unvegetated clearly showing sand splays from occasional overwashes from the south.

Raccoon Island, 180-m altitude. Central portion of island unprotected by breakwaters. Vigorous vegetative growth--mostly mangroves, but also some Spartina patens and Spartina alternifolia grasses--covers much of the island.

Raccoon Island, 180-m altitude. Eastern portion of island protected by breakwaters. Some patches of mangroves are dead and defoliated on the interior lagoons, likely because of high concentrations of guano.

Raccoon Island, 180-m altitude. View of entire island from low-oblique.

Raccoon Island, 180-m altitude. Low-oblique photos of southern shore. Flying birds, especially brown pelicans, can be seen in most of this series.

Close-up photographs of nesting pelicans. Note the dead mangroves.

Bay Junop USGS research site.

Old Oyster Bayou USGS research site.