In the following, we present six examples of how the archival materials have been used to address both scientific and resource management questions.

Lake Okeechobee: 1928 and 2004

Lake Okeechobee has been called the hydrologic lynchpin of the Everglades (Light and Dineen 1994). Historically, it received water from the Kissimmee River to the north and released water via sheetflow to the Everglades to the south (Figure 16.2). By the early 1900s, farming had begun in the peat-lands south of the lake (Snyder and Davidson 1994). In September 1928, a category four hurricane passed just to the northeast. The resulting winds drove the lake's water southward, overtopping its banks, and drowning over 2,000 people in the small farm towns along the south shore (Mitchell 1928). Subsequently, an extensive dike system was built which totally surrounded Lake Okeechobee. Included in the engineering were four large pump stations at the outlets of the major drainage canals to the south. Water management was implemented that lowered Lake Okeechobee's water levels by 2m to prevent future flooding. Wetland vegetation colonized the exposed lake bottom and today extensive marshlands are located along the western and southwestern shorelines (Figure 16.3).

Figure 16.2: The State of Florida is shown above and the greater Everglades ecosystem in south Florida is enlarged below. Inset boxes give the approximate positions, and figure numbers, for the remaining figures in this chapter. [larger image]

Figure 16.3: Shown is an region on the southwestern shore of Lake Okeechobee. The geo-referenced 1928 T-sheet (#4128) is draped over the 2004 DOQQs. In 1928, Observation Island, was in fact, an island. Today it is surrounded by extensive marshes that are clearly visible in the 2004 aerial photography. (Scale 1:50,000) [larger image]

Captiva and Sanibel Islands: 1859 and 2004

These barrier islands form a reverse J-shape arc on the southwest coast of Florida (Stapor et al. 1991, see fig. 2), and are relatively low-lying with distinctive, linear, beach-ridge systems. The coast is characterized as low wave energy with low sediment supply (Haung and Goodell 1967). The oldest portions of the islands date to 3,000 YBP (Stapor et al. 1991). Stapor et al. (1991) discuss the islands' stability over the past 3,000 years, including that of the passes that separate them. However, they make no comment concerning Redfish Pass. In examining the historical charts, it became clear that Redfish Pass was closed in 1859 (Figure 16.4a) and that Captiva was a single island, not the North and South Captiva Islands of today. A nearby inlet was opened during the passage of Hurricane Charley in August 2004 (Sallenger et al. 2006). Major hurricanes crossed Charlotte Harbor area in 1873, 1894, 1910, 1926, and 1944 (Anonymous 1873; Dunn and Miller 1964) and may have been responsible for opening Redfish Pass, since they are known to play an important role in inlet dynamics (Leatherman 1988). While this area of Captiva Island has undergone major changes, shorelines of nearby Sanibel Island have remained relatively unchanged (Figure 16.4b). This is true for both the Gulf of Mexico shoreline and the estuarine shorelines on the backside of the island. The hurricanes which impacted Captiva also struck Sanibel. The one obvious difference between the two islands is their orientation, with Captiva's being 170°(approximately north-to-south), and Sanibel's is much more east-to-west at 100°. These differing orientations would mean differing exposures to waves, and subsequent erosion, during the passage of a hurricane.

Figure 16.4: This figure shows two nearby regions of Sanibel and North Captiva Islands on Florida's west coast. Geo-referenced charts from 1859 are superimposed on the 2004 baseline aerial images. Major changes are clearly visible between times in the upper panel depicting North Captiva Island. Redfish Pass (lower arrow) was clearly closed in 1859. The upper black arrow points to a breech in the island that was caused by storm overwash and erosion during the passage of Hurricane Charley in August 2004. The estuarine shorelines (black arrows in lower panel) of Sanibel Island, 15km to the southeast, have undergone little change. (Scale 1:50,000) [click on images above for larger versions]

Historic and modern shorelines in the southwest Everglades: 1888/9 and 2004

The Gulf of Mexico shoreline of the southwest Everglades coast, from Cape Romano to northwest Cape Sable, was published in a series of five charts in 1888-89 (Figure 16.5 and Figure 16.6; not all charts are shown). Comparison with modern shorelines has revealed interesting patterns. In the northern portion of the study area, little change has occurred (Figure 16.5). Shoals that were demarcated on the 1888 chart are clearly visible on the 2004 aerial photographs in very nearly the same locations. In the southern portion of the area, particularly at the mouth of the Shark River, major differences are apparent (Figure 16.6). The shoreline has retreated landward by over 500m in some cases. Why would these two areas differ in their history since 1888? Although sea level has been rising along this coastline since the 1840s (Maul and Martin 1995) it has not varied along the coast. Both portions of the coast have been impacted by approximately the same number and strength of land-falling hurricanes. The northern area may receive some protection from the Cape Romano shoals which are a few kilometers offshore (Holmes and Evans 1963). A more likely explanation is differences in surficial geology between these areas. The northern and southern 10,000 Islands are very distinct physiographic regions (Parkinson 1989). The small islands of the northern 10,000 Islands often are fringed by hard oyster and vermetid worm reefs (Scholl 1964) resistant to erosion, whereas the mangrove islands in the mouth of the Shark River consist of deep organic peats (Spackman et al. 1977), a substrate that may be more easily eroded.

Figure 16.5: This figure shows an area in the northern 10,000 Islands. Chart T-1836 from 1888 is overlain onto 2004 aerial photographs. Positions of shoals and reefs (white arrows) and mangrove forest shorelines (black arrows) have changed little in the 116 year interval. (Scale 1:24,000) [larger image]

Figure 16.6: This figure shows an area in the southern 10,000 Islands at the mouth of the Shark River. Chart T-1903 from 1889 is overlain onto 2004 aerial photographs. Major erosion and coastal set-back of the mangrove islands is clearly evident. Upper line is 250m and the lower white line 500m. (Scale 1:24,000) [larger image]

Habitat change on southern Cape Sable: 1857, 1928 and 2004

Figure 16.7: This figure shows a region of south central Cape Sable. The 1857 T-sheet (#649) is overlain on 2004 aerial photographs. The 1857 shoreline has been digitised and appears as a bold black line (dashed arrow). The symbols on the chart clearly delineated mangrove forest (solid white arrows) from marsh (blue arrows). (Scale 1:24,000) [larger image]

Figure 16.8: This figure shows the same area as in Figure 16.7. Here however chart T-4460, based on 1928 air photos, is overlain on the 2004 aerials. Major changes are readily apparent with marsh habitats in 1928 becoming open water (blue arrows) or mangrove forest (white arrows). The dashed white arrow points to two canals constructed in the early 1920s. (Scale 1:24,000) [larger image]

Vanishing islands in Whitewater Bay, six snapshots in time: 1928, 1940, 1952, 1964, 1987 and 2004

Whitewater Bay lies between the Florida mainland and Cape Sable. It is an important habitat for a variety of endangered (e.g. Florida Manatee, Smalltooth Sawfish) and recreationally important fish species (e.g. Mangrove Snapper, Redfish). The Bay is also dotted with low elevation, mangrove-forested islands of various sizes. Some islands are >1,000ha in area and many are <1ha in size. In conducting over 20 years of research in south Florida and having made numerous trips in and through Whitewater Bay we noticed that smaller mangroves islands in the Bay were disappearing (T. J. Smith, pers. obs.). We have just begun to use the resources within the EHAP project to address this phenomenon. Our interest is to determine where in the bay islands are being lost, how many have disappeared, determine when they disappeared, and if possible to develop hypotheses as to why they have vanished. As an example, we mapped a small area in the southeast portion of Whitewater Bay for six time periods. We initially hypothesized that the period of island loss would correspond to the period of high hurricane activity mentioned above. This was not the case. Most islands appear to have disappeared between 1987 and 2004 (Figure 16.9). Although Hurricane Andrew struck in 1992, it passed well north of Whitewater Bay and few environmental impacts were noted in the Bay (Smith et al. 1994). At present, we are revising the initial hypothesis for this portion of our work, and are confident that continued analysis of historic charts and aerial photographs will aid in this endeavor.

Figure 16.9: A small area of southeastern Whitewater Bay is shown here at six points in time. Two small mangrove islands and a narrow mangrove forest peninsula are indicated in 1928. The two islands can be found through 1987, however between 1987 and 2004 they have disappeared. The mangrove peninsula shows a steady erosion and decrease in size over the entire time period. [larger image]

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