Off-Road Vehicle Trail Accuracy Assessment: Big Cypress National Preserve (BICY) Final Report

Transcription

1 Off-Road Vehicle Trail Accuracy Assessment: Big Cypress National Preserve (BICY) Final Report By Roy Welch, Marguerite Madden and Thomas Litts Center for Remote Sensing and Mapping Science (CRMS) The University of Georgia February 20, 2001

2 Off-Road Vehicle Trail Accuracy Assessment: Big Cypress National Preserve (BICY) Final Report By Roy Welch, Marguerite Madden and Thomas Litts Center for Remote Sensing and Mapping Science (CRMS) The University of Georgia Athens, Georgia Final Report Submitted to: U.S. Department of Interior National Park Service Big Cypress National Preserve Ochopee, Florida Cooperative Agreement February 20,

3 Table of Contents Page List of Figures 3 List of Tables 5 Abstract 6 Introduction 6 Study Area 9 Accuracy Assessment Methodology 9 ORV Trail Accuracy Assessment Results 14 Quadrangles with ORV Access 17 Quadrangles Closed to ORVs 26 Comparison of Mapped and Helicopter/Field- 26 Verified ORV Trail Classes Estimate of New Trails Crossing Transects 28 Revised Estimate of ORV Trail Length 28 Conclusion 33 Acknowledgments 34 References 35 2

4 List of Figures Figure Description Page 1 Index map of USGS 7.5-minute topographic quadrangles 8 covering Big Cypress National Preserve (BICY). 2 Hand-held digital images of ORV trails crossing (a) prairie; 10 (b) cypress forest and savanna; and (c) pine savanna vegetation communities in BICY. 3 Sample of four helicopter flight transects created across 11 the Burns Lake quadrangle. 4 Bell Jet Ranger 206 helicopter equipped with a Coast Guard 13 Beacon receiver mounted on an exterior bracket. 5 Field measurements of tertiary (a) and secondary (b) ORV 13 trails. 6 Hand-held digital camera images and scanned 35-mm 15 film photographs taken during helicopter/gps surveys to document current conditions of ORV trails. 7 Examples of ORV trail classifications: (a) active tertiary trails; 16 (b) old tertiary trails; (c) secondary trail; (d) primary trails; (e) high impact area; and (f) braided trails forming a high impact area. 8 Results from the ORV trail database accuracy assessment using 18 helicopter/field surveys and GPS. 9 ORV trail observed points color-coded according to accuracy 19 assessment results Burns Lake. 10 ORV trail observed points color-coded according to accuracy 20 assessment results California Slough. 11 ORV trail observed points color-coded according to accuracy 21 assessment results Deep Lake. 3

5 List of Figures (Continued) Figure Description Page 12 ORV trail observed points color-coded according to accuracy 22 assessment results Lostmans Trail. 13 ORV trail observed points color-coded according to accuracy 23 assessment results Monroe Station. 14 ORV trail observed points color-coded according to accuracy 24 assessment results Thompson Pine Island. 15 Digital images depicting (a) game trails; (b) a survey line; and 25 (c) the lack of evident ORV trails north of the Loop Road and heavy ORV impact south of the Loop Road in the Monroe Station quadrangle area. 16 True color digital image (green vegetation) of 2000 ORV trails 30 registered to a 1994 USGS color infrared DOQQ (red vegetation). 17 ORV Management Unit boundaries in BICY. 32 4

6 List of Tables Table Description Page 1 ORV trail classes identified in helicopter/field surveys Ground measurements of ORV trail classes Tabulation results from the ORV trail accuracy 17 assessment. 4 Comparison of ORV trail classes mapped from the /1995 air photos with the trail classes noted for the same points during the May 2000 helicopter surveys. 5 Mapped tertiary trails identified in 2000 helicopter/field 29 surveys as ORV trail classes (1 10). 6 Adjusted ORV trail length. 31 5

7 Off-Road Vehicle Trail Accuracy Assessment: Big Cypress National Preserve (BICY) Abstract The Center for Remote Sensing and Mapping Science (CRMS) at The University of Georgia was asked by the National Park Service (NPS) to assess the accuracy of offroad vehicle (ORV) trail maps and a corresponding digital database for Big Cypress National Preserve (BICY). These products were produced in from U.S. Geological Survey (USGS) National Aerial Photography Program (NAPP) color infrared aerial photographs recorded in 1994/1995. Areas corresponding to six USGS 7.5-minute quadrangles within BICY were selected for accuracy assessment using a helicopter and Global Positioning System (GPS) navigation systems to verify trail locations and classes noted on the maps. Nearly 1500 observed points (approximately 250 per quadrangle) were recorded from the helicopter or in the field. These points were input to a geographic information system (GIS) database and the ESRI ArcView software package employed to color-code trail classifications and assess their accuracy with respect to the ORV trail maps. In the four quadrangles open to ORV use (Burns Lake, California Slough, Lostmans Trail and Thompson Pine Island), the percent of correctly mapped ORV trails ranged from 93.1 to 73.9 percent for individual quadrangles and 82.4 percent correct for all four quadrangles combined. In the two quadrangles where ORV use has been historically closed for approximately 20 years, however, only 44.9 percent of the previously mapped ORV trails were identified from the helicopter. In these restricted-use areas, about 15 percent of the observed points were identified as Other Trails (e.g., game trails and survey lines) and at the remaining 40 percent no trails could be detected from the helicopter - possibly due to vegetation regrowth and recovery following ORV exclusion. Based on this accuracy assessment, the total length of trails in BICY Preserve as mapped from the aerial photographs was revised downward from 47,958 to 37,346 km. This new figure takes into account game trails/trail recovery and is believed to be a good estimate of total ORV trail length in BICY. Introduction The dramatic increase in recreational off-road vehicle (ORV) use within Big Cypress National Preserve (BICY) and the consequent impact on the environment has generated considerable controversy between ORV user groups, environmentalists, state resource agencies and the National Park Service (NPS) (Daniel, 1999; Staats, 1999; Christian, 2000; Daerr, 2000). Originally used for logging, farming and oil exploration activities, ORVs are now primarily associated with hunting and recreational activities (Tebeau, 1966; Duever, et al., 1986a). Consequently, the NPS has undertaken the development of a management plan designed to minimize the impact of ORV use on the 6

8 environment. A requirement for their plan has been information on trail locations and summary statistics documenting the magnitude of ORV use. In their investigation of ORV impacts in BICY, Duever, et al. (1981; 1986a; 1986b) mapped ORV trails from aerial photographs acquired in 1940, 1953 and Although these maps are valuable records of historical ORV use in BICY, they do not document the increased use of ORVs that has occurred within the Preserve over the past decade. An Arc/Info ORV trail database registered to the Universal Transverse Mercator (UTM) ground coordinate system and tied to the North American Datum of 1983 (NAD 83) was produced in by the CRMS as part of NPS Cooperative Agreement (Welch, et al., 1995; 1999). Trails were plotted at 1:15,000 scale from U.S. Geological Survey (USGS) National Aerial Photography Program (NAPP) color infrared aerial photos of 1:40,000 scale (enlarged to 1:10,000 scale) recorded in the winter months of 1994 and 1995 (Welch and Madden, 1998). When the photos were recorded, canopy cover was minimal and heavy rainfall had flooded many of the trails, accentuating their visibility on the air photos. The objective of this study was to assess the reliability of these ORV trail maps and to produce the following products for areas corresponding to six USGS 7.5-minute topographic quadrangles representative of the various terrain and conditions for ORV use within BICY (Figure 1). 1) An estimate of the overall accuracy of the ORV trail database for BICY, along with specific accuracy values for the CRMS 1:15,000-scale maps covering the Burns Lake, California Slough, Deep Lake, Lostmans Trail, Monroe Station and Thompson Pine Island USGS quadrangles. 2) Information on the reliability of the ORV trail class designations employed on the maps and the likelihood of linear features (e.g., large game animal trails and survey lines) being misidentified as ORV trails. 3) A pictorial database of digital images documenting the accuracy assessment process and illustrating the conditions in the field. 4) ORV trail maps for the six quadrangles on which the observed/sample point locations are superimposed and color-coded to indicate correctness of classification. 5) An estimate of new trails created since 1994/ the date of the aerial photographs used to produce the ORV trail database. 6) An adjustment to the total length of ORV trails in BICY based on the results of the accuracy assessment. 7

9 Figure 1. Index map of USGS 7.5-minute topographic quadrangles covering BICY. The Preserve boundary is delineated in green and the six quadrangles selected for the ORV trail accuracy assessment are shaded in blue. 8

10 In order to meet these objectives, the CRMS and the NPS used a combination of remote sensing, geographic information system (GIS) and Global Positioning System (GPS) technologies with helicopter/field surveys to assess the accuracy of ORV trails mapped in BICY. Study Area Big Cypress National Preserve occupies 2,950 km 2 in southwest Florida just north of Everglades National Park. It is an area of extensive cypress forest, pine savanna and graminoid prairies. The Preserve was created in 1974 within the framework of the National Park System to manage human activities such as hunting, fishing, trapping, oil and gas exploration, grazing and the use of motorized vehicles - while maintaining the natural, recreational and aesthetic values of the area (Deuver, et al., 1986a). Much of the area is inaccessible by roads and users of the Preserve rely heavily on ORVs to access private in-holdings in BICY and for recreational activities. The terrain of BICY is flat with vegetation consisting of a complex mix of temperate and tropical plant species. Between 1994 and 1998, the CRMS worked cooperatively with the NPS to map vegetation communities in BICY as part of a project to develop a detailed vegetation database for National Parks/Preserves in south Florida (Welch, et al., 1995; Welch and Remillard, 1996; Welch, et al., 1999). The impacts of ORVs on BICY vegetation were addressed during the development of the 1994/1995 ORV trail database (Welch and Madden, 1998). A GIS analysis of the spatial coincidence between ORV trails and vegetation communities in BICY revealed trails cross many different vegetation types from hardwood forests and mangrove scrub to open prairies. Graminoid prairies were impacted most by ORV trails, followed by cypress forest, cypress savanna and pine savanna areas (Figure 2). Accuracy Assessment Methodology An accuracy assessment of the 1994/1995 ORV trail database was conducted in May of 2000 using a combination of helicopter/field surveys, remote sensing, GIS and GPS techniques. Four transects, approximately 15 to 20 km in length, were defined across each quadrangle two in a north-south direction and two in an east-west direction (Figure 3). Each transect contains multiple three- to four-kilometer segments that zig-zag and cross as many trails as possible. Surveys were conducted along each transect with the aid of a Bell Ranger 206 helicopter occupied by two CRMS personnel, a BICY botanist who acted as an observer and the helicopter pilot. The pilot flew along the transects which were defined by latitude/longitude coordinates logged into the helicopter GPS navigation unit prior to each flight. In addition, a laptop computer was linked to a Trimble Pro XRS GPS unit with a Coast Guard beacon antenna mounted on an exterior 9

11 a. b. c. Figure 2. Hand-held digital images of ORV trails crossing (a) prairie; (b) cypress forest and savanna; and (c) pine savanna vegetation communities in BICY. 10

12 Figure 3. Sample of four helicopter flight transects created across the Burns Lake quadrangle. 11

13 bracket attached to the helicopter (Figure 4). The computer-gps combination provided differentially corrected coordinates accurate to within a few meters, and allowed the track of the helicopter to be continuously displayed on a digital map of ORV trails. As the helicopter passed over the intersections of the ORV trails with the transect, (i.e., the observed points), the CRMS and BICY personnel jointly determined if the trail was obviously created by ORVs, the ORVs were using an existing road, the trail appeared to be some other linear feature such as a game trail or survey line, or there was no evidence of a trail (Table 1). If the trail was deemed an ORV trail, it was classified as primary, secondary or tertiary and a note was made if the trail appeared to be abandoned. These classes are based on field measurements of trail width as noted below in Table 2 and depicted in Figure 5. Table 1. ORV trail classes identified in helicopter/field surveys. ORV Class ORV Trail Class Description 1 Primary Trail 2 Secondary Trail 3 Tertiary Trail 4 High Impact Area 5 Potential High Impact Area 6 Other Trail (e.g., Game Trail) 7 Road 8 Old Tertiary Trail 9 No Trail Evident 10 Old High Impact Area Table 2. Ground measurements of ORV trail classes. ORV Trail Class Width on the Ground (meters) * (1) Primary >10 to 20 (2) Secondary >5 to < 10 (3) Tertiary 2 to < 5 * These trail width parameters are slightly narrower than those noted for primary, secondary and tertiary classes on the original ORV trail maps compiled from the air photos. 12

14 Figure 4. Bell Ranger 206 helicopter equipped with a Coast Guard beacon receiver mounted on an exterior bracket. a. Figure 5. Field measurements of tertiary (a) and secondary (b) ORV trails. b. 13

15 All observations were stored in a digital database. During the flights and at regular intervals along the transects, photographs were taken with a 35-mm film camera and digital images with a Kodak Digital Science Field Imaging System (FIS) 265. The hand-held Kodak digital camera was connected to a Garmin III Plus GPS that stamped the location, time and date on each image. Selective Availability (SA), introduced by the Department of Defense to degrade GPS signals in the interest of national security, was terminated on May 1, Since our work began on May 2 nd, the uncorrected GPS locations recorded by the Garmin receiver and stamped on the digital images were found to be accurate to within approximately + 10 m (compared to m with SA) (Hurn, 1993). These images, along with those scanned from the 35-mm film, were input to ArcView to provide a pictorial record of approximately 300 field observations that document the validation process, depict current conditions of trails in BICY and illustrate the ORV class designations (Figures 6 and 7). The majority of the trails in BICY are narrow (2 < 5 m wide) tertiary trails with a double track of exposed soil and vegetation growing between the tracks (Figure 7a). Although these trails were usually visible beneath the helicopter, old abandoned trails that have vegetation growing in the tracks were sometimes difficult to detect (Figure 7b). Along routes heavily used by ORVs, the trails become wider (>5 to < 10 m), more rutted and devoid of vegetation (Figure 7c). In a few cases, trails were >10 m in width and were designated as primary trails (Figure 7d). Areas of concentrated ORV use mapped as high impact polygons in the ORV database were identified by multiple tertiary and secondary trails converging in an area or appearing as braided trails (Figures 7e and 7f). ORV Trail Accuracy Assessment Results The number of observed points along transects within each quadrangle are listed in Table 3 and as (a) in Figure 8, and ranged from 232 for Burns Lake to 260 for Monroe Station - for a total of 1487 observed points. The proportion of observed points classed as: (b) ORV Trails; (c) Roads Used by ORVs; (d) Other Trails; or (e) No Trails Visible are also provided in both Table 3 and Figure 8. The locations of transects and observed points for each of the six quadrangles are presented in Figures 9 through 14. Since only four of the six quadrangles involved in the accuracy assessment currently permit ORV use, the results of the accuracy assessment are discussed below in two sections: 1) quadrangles with ORV access; and 2) quadrangles closed to ORV access. 14

16 Figure 6. Hand-held digital camera images and scanned 35-mm film photographs taken during helicopter/gps surveys to document current conditions of ORV trails. 15

17 a. b. c. d. e. f. Figure 7. Examples of ORV trail classifications: (a) active tertiary trails; (b) old tertiary trails; (c) secondary trail; (d) primary trails; (e) high impact area; and (f) braided trails forming a high impact area. 16

18 Quadrangles with ORV Access (Burns Lake, California Slough, Lostmans Trail and Thompson Pine Island) In areas where ORV use is permitted, the percent of observed points that were mapped as ORV trails and noted as active or abandoned ORV trails during the helicopter surveys ranged from 93.1 percent for Burns Lake to 73.9 percent for Thompson Pine Island (see Table 3). A small percentage of mapped ORV trails were noted as roads used as ORV trails (e.g., 2.6 percent in Burns Lake and 2.8 percent in California Slough). Also, a small percentage of the previously mapped ORV trails were categorized as Other Trails which included game trails and survey lines (11.6 percent and 9.8 percent in the case of Lostmans Trail and Thompson Pine Island, respectively) (Figures 15a and 15b). The percentage of observed points for which no ORV, roads or other trails were visible within quadrangles open to ORV use ranged from 16.3 percent for Thompson Pine Island (due to pine and cypress tree cover obscuring the ground) to 3.0 percent for Burns Lake. Table 3. Tabulation results from the ORV trail accuracy assessment. Quadrangle Name # Observed Points ORV Trails (%) Roads Used by ORVS (%) Other Trails (%) No Trails (%) a) Burns Lake b) California Slough c) Lostmans Trail d) Thompson Pine Island e) Deep Lake* f) Monroe Station* Quadrangles with ORV Access (a-d) Quadrangles closed to ORVs (e-f) *ORV use is restricted in Deep Lake and Monroe Station quadrangles. 17

19 Figure 8. Results from the ORV trail database accuracy assessment using helicopter/field surveys and GPS. 18

20 Figure 9. ORV trail observed points color-coded according to accuracy assessment results Burns Lake. 19

21 Figure 10. ORV trail observed points color-coded according to accuracy assessment results California Slough. 20

22 Figure 11. ORV trail observed points color-coded according to accuracy assessment results Deep Lake. 21

23 Figure 12. ORV trail observed points color-coded according to accuracy assessment results Lostmans Trail. 22

24 Figure 13. ORV trail observed points color-coded according to accuracy assessment results Monroe Station. 23

25 Figure 14. ORV trail observed points color-coded according to accuracy assessment results Thompson Pine Island. 24

26 . Game Trail a. Survey Line b. Loop Road N c. Figure 15. Digital images depicting: (a) game trails; (b) a survey line; (c) the lack of evident ORV trails north of the Loop Road and heavy ORV impact south of the Loop Road in the Monroe Station quadrangle area. 25

27 Quadrangles Closed to ORVs (Deep Lake and Monroe Station) Off-road vehicle use has been historically restricted in the Deep Lake and Monroe Station quadrangles and only 48.8 and 41.1 percent of the mapped ORV trails could be identified as ORV trails from the helicopter (see Table 3). Other trails - mainly game trails in Deep Lake and a mix of game trails and old survey cuts or possibly logging tram lines in Monroe Station, accounted for 15.1 and 15.8 percent of the observed points, respectively. A considerable proportion of the mapped ORV trails in Deep Lake (35.3 percent) and Monroe Station (43.1 percent) were not visible. Although further investigation is required to determine the origin of linear features identified on the aerial photographs and mapped as ORV trails within the Deep Lake and Monroe Station (inside the Loop Road) restricted areas, it is possible that very old ORV trails, survey cuts and tram lines are visible on the 1994/1995 aerial photos but not from the helicopter due to vegetation regrowth. Figure 15c depicts the contrast in trail visibility inside (north of Loop Road) and outside (south of Loop Road) of the ORV exclusion area in the Monroe Station quadrangle. Comparison of Mapped and Helicopter/Field-Verified ORV Trail Classes Information on the reliability of ORV trail class designation and the likelihood of misidentifying other linear features (such as large game animal trails) with trails created by ORVs was obtained by comparing mapped ORV trail classes with helicopter/fieldverified classes for all 1487 observed points (Table 4). Although only two of the observed points were designated as primary trails in the ORV database, one was verified from the helicopter as being correctly identified and the other was verified as being included in a high impact area. Over half (53 percent) of the secondary trails also were correctly designated as secondary trails or were incorporated into high impact areas by May Roads were designated as secondary trails 38.2 percent of the time because dirt roads in BICY and secondary ORV trails are of similar width and ORVs often travel on these roads. A small percentage of the observed points mapped as secondary trails were misclassified as tertiary trails (5.9 percent) and one secondary trail was not visible from the helicopter. The majority of the observed points were mapped as tertiary trails. By 2000, 15.7 percent of the points mapped as tertiary trails were identified from the helicopter/field surveys as being secondary trails or high impact areas (see Table 4). Nearly 52 percent were correctly identified as active or abandoned tertiary ORV trails. Only two tertiary trails were actually roads. Other trails and linear features such as game trails and section lines were confused with mapped tertiary trails 10.4 percent of the time and 22 percent of the tertiary trails were not visible from the helicopter. Over 57 percent of the mapped high impact areas were identified as active or recovering high impact areas during the helicopter/field surveys (see Table 4). Three 26

28 2000 Helicopter/Field-Verified ORV Trail Classes Mapped ORV Trail Classes Primary Trail (Class1) Second. Trail (Class 2) Tertiary Trail (Class 3) High Impact Area (Class 4) Other Trail (Class 6) Road (Class 7) Old Tertiary Trail (Class 8) No Trail (Class 9) Old High Impact (Class10) Total Primary Trail (Class 1) 50% [1]* 50% [1] 100% [2] Secondary Trail (Class 2) 41.2% [14] 5.9% [2] 11.8% [4] 38.2% [13] 2.9% [1] 100% [34] Tertiary Trail (Class 3) 2.3% [27] 30.9% [362] 12.2% [143] 10.4% [122] 0.2% [2] 20.8% [244] 22.0% [258] 1.2% [14] 100% [1172] High Impact Area (Class 4) 0.4% [1] 2.6% [7] 10.2% [27] 41.9% [111] 7.5% [20] 8.7% [23] 13.2% [35] 15.5% [41] 100% [265] Potential High Impact (Class 5) 14.3% [2] 21.4% [3] 21.4% [3] 28.6% [4] 14.3% [2] * Note, number of observation points indicated by [ ]. 100% [14] Table 4. Comparison of ORV trail classes mapped from the 1994/1995 air photos with the trail classes noted for the same points during the May 2000 helicopter surveys. 27

29 percent of the high impact areas were deemed to be primary or secondary trails, while nearly 19 percent were identified as tertiary trails. The remaining high impact observed points were actually other trails (7.5 percent) or no trails were visible (13.2 percent). A total of 14 points were originally mapped as potential high impact areas - questionable because the air photo was dark due to wet conditions at the time the photo was taken. The majority of these points (12) were verified as high impact areas, secondary trails, tertiary trails or old tertiary trails, while two showed no evidence of ORV use. Estimate of New Trails Crossing Transects It was not possible to simultaneously conduct the accuracy assessment and record new trails during the same helicopter flight. Since funds did not permit flying all transects twice, an estimate of new trails was accomplished in the following manner. For each quadrangle, the results of the accuracy assessment were examined to tally the helicopter/field-verified classes of observed points originally mapped as narrow tertiary trails (Class 3) in the ORV database (Table 5). Points mapped as Class 3, but verified as either wide primary (Class 1) trails, secondary (Class 2) trails or high impact areas (Class 4), indicate an increase in ORV activity between 1994/1995 and May Based on this assumption, results indicate Burns Lake and California Slough exhibited the greatest degree of new ORV trails with 52 percent and 21 percent, respectively, of the mapped tertiary trails being verified as secondary trails or high impact areas in Thompson Pine Island likewise showed a 10 percent increase in trails. Less than 10 percent of the observed points were verified as primary, secondary or high impact in the Monroe Station (3.5 percent), Deep Lake (2.5 percent) and Lostmans Trail (0.5 percent) quadrangles, indicating relatively few new trails in these areas. In addition to the examination of accuracy assessment results, a photogrammetric method of estimating new trails was tested. Figure 16 demonstrates the potential for warping or rubber sheeting the hand-held digital camera images acquired during the helicopter surveys to the 1994/1995 USGS orthorectified DOQQs. Using this technique, new trails can be mapped for selected areas and compared to the trails contained in the 1994/1995 ORV database. Although it is recognized that this method is not practical for updating the entire database, it is useful in assessing new ORV trails in sample areas. Revised Estimate of ORV Trail Length Based on the results of the ORV accuracy assessment, the total trail length of ORV trails within the six-quadrangle study area was adjusted by applying the percentage of observed points noted as ORV trails in each quadrangle (or ORV accuracy) to the total 28

30 2000 Helicopter/Field-Verified ORV Trail Classes Tertiary Trails Mapped in BICY Quads Primary Trail (Class 1) Second. Trail (Class 2) Tertiary Trail (Class 3) High Impact Area (Class 4) Potential High Impact (Class 5) Other Trail (Class 6) Road (Class 7) Old Tertiary Trail (Class 8) No Trail (Class 9) Old High Impact (Class10) Total Burns Lake 5.5% [10]* 35.2% [64] 46.2% [84] 1.6% [3] 4.4% [8] 3.8% [7] 3.3% [6] 100% [182] California Slough 4.3% [9] 48.3% [102] 17.1% [36] 1.9% [4] 0.9% [2] 13.3% [28] 14.2% [30] 100% [211] Deep Lake 0.6% [1] 3.1% [5] 1.9% [3] 15.4% [25] 32.7% [53] 44.4% [72] 1.9% [3] 100% [162] Lostmans Trail 0.5% [1] 30.2% [64] 13.7% [29] 47.6%** [101] 6.6% [14] 1.4% [3] 100% [212] Monroe Station 10.2% [23] 3.5% [8] 17.7% [40] 23.0% [52] 44.7% [101] 0.9% [2] 100% [226] Thompson Pine Island 3.4% [6] 58.1% [104] 6.7% [12] 11.7% [21] 1.1% [2] 19.0% [34] 100% [179] * Note, number of observation points indicated by [ ]. ** Trails that appeared old in Lostmans Trail may be airboat trails. Table 5. Mapped tertiary trails identified in 2000 helicopter/field surveys as ORV trail classes (1 10). 29

31 Figure 16. True color digital image (green vegetation) of 2000 ORV trails registered to a 1994 USGS color infrared DOQQ (red vegetation). 30

32 length of ORV trails depicted on the maps prepared from the 1994/1995 air photos (Table 6). The total length of ORV trails in the six quadrangles is therefore reduced from 16,217 km to an estimated 10,977 km. Table 6. Adjusted ORV trail length. Quadrangle Name Mapped ORV Trail Length (km) ORV Accuracy (%) Adjusted ORV Trail Length (km) Burns Lake California Slough Lostmans Trail Thompson Pine Island Deep Lake Monroe Station Total UGA-CRMS The estimate of ORV trail length for the entire BICY Preserve was revised using two accuracy values - one for areas with ORV access and one for areas closed to ORV use. An accuracy value of 82.4 percent was derived for areas open to ORV access by dividing the total number of observed points noted as ORV trails (803) by the total number of observed points (975) in the four quadrangles where ORV access is permitted (Burns Lake, California Slough, Lostmans Trail and Thompson Pine Island). For areas closed to ORVs, the number of observed points noted as ORV trails (230) divided by the total number of observed points in the Deep Lake and Monroe Station quadrangles (512), provided an accuracy value of 44.9 percent. These two accuracy values were then applied to ORV trail length as tallied by ORV Management Units. The ORV Management Units in which access by ORVs is permitted include the West Addition Area, Bear Island, Northeast Addition Area, Turner River, Corn Dance and Stairsteps Management Units (Figure 17). Total trail length for these units as depicted on the original ORV trail maps is 42,169 km. This figure is reduced to an estimated 34,747 km when multiplied by 31

33 Figure 17. ORV Management Unit boundaries in BICY. 32

34 82.4 percent. Similarly, the mapped trails in the ORV Management Units closed to ORVs totaled 5,789 km. Application of the 44.9 percent accuracy figure as noted above reduces the length of trails in the Deep Lake and Loop Units to an estimated 2,599 km. A summation of these estimates (34, ,599 km) provides an updated ORV trail length of 37,346 km for BICY, as compared to the 47,958 km determined from the original mapping effort. While this estimate of ORV trail length may be subject to further revision based on accuracy assessments of ORV trails in the remaining 25 quadrangles, any major changes to the current estimate are thought to be unlikely. Conclusion An assessment of the accuracy of an ORV trail database in BICY was accomplished using helicopter/field surveys in combination with remote sensing, GPS and GIS techniques. For a sample area corresponding to six quadrangles within BICY, nearly 1500 observed points were collected, along with 35-mm slides and images recorded by a Kodak digital camera to document current conditions of the ORV trails. Results of the helicopter/field surveys indicated 82.4 percent of the mapped ORV trails were correct in four quadrangles with ORV access, with individual quadrangles ranging from 93 to 74 percent correct. In areas where ORV access has been historically closed, such as the Deep Lake and Monroe Station quadrangles, only 44.9 percent of the previously mapped ORV trails could be located during the helicopter surveys. Approximately 15 percent of the observed points were identified as Other Trails (e.g., game trails and survey lines) and another 40 percent were not visible from the helicopter. Further investigation to determine if mapped ORV trails in these restricted areas are visible on historical aerial photographs may be warranted to establish whether these trails have recovered to the point where tracks are not visible from the air. Examination of the reliability of ORV trail class designation in all six quadrangles showed 53 percent of the mapped secondary trails were identified as secondary trails or as part of high impact areas on the ground, while 38 percent were roads used by ORVs. Less than 10 percent of the secondary trails were misclassified as tertiary trails or not visible from the helicopter. Tertiary trails, constituting the majority of ORV trails in BICY, were verified as active or abandoned tertiary trails for nearly 52 percent of the observed points with another 16 percent identified from the helicopter as secondary or high impact areas, indicating possible areas of increased ORV use. Ten percent of the tertiary trails were actually game trails/survey lines and 22 percent were not visible on the ground, possibly due to vegetation regrowth in ORV exclusion areas. Over 57 percent of the high impact areas were verified in the helicopter surveys, nearly 22 percent were primary, secondary or tertiary trails and the remaining 21 percent were actually other trails (7.5 percent) or were not visible (13 percent) from the helicopter. An estimate of new trails crossing transects based on the results of the accuracy assessment indicated the greatest increase in ORV use in the Burns Lake quadrangle 33

35 where 53 percent of the observed points mapped as tertiary trails from the 1994/1995 air photos were identified as secondary trails or high impact areas in May Likewise, accuracy assessment results in California Slough and Thompson Pine Island showed a 21 and 10 percent increase, respectively, in ORV activity. The remaining quadrangles (Monroe Station, Deep Lake and Lostmans Trail) had less than 10 percent of the observed points originally mapped as tertiary trails were verified as secondary trails/high impact areas indicating relatively few new trails in these quadrangles. Based on the results of the ORV accuracy assessment for the six quadrangles, the estimate of ORV trail length for the entire preserve was revised. Applying a figure of 82.4 percent to the total length of ORV trails in BICY ORV Management Units open to ORV traffic and 44.9 percent to Management Units with restricted ORV access, the total trail length was reduced from 47,958 km noted in the original mapping effort to 37,346 km. It is anticipated that the information presented here will be used by NPS managers of BICY to assist in the management of ORV use in the Preserve. The ORV database also provides a baseline of information for monitoring the effectiveness of future ORV regulations. A combination of management strategies and increased awareness by BICY visitors will permit the continued use of ORVs while minimizing impacts on natural resources of the Preserve. Acknowledgments This study was sponsored by the U.S. Department of Interior, National Park - Service (NPS), Cooperative Agreement Technical assistance was provided by the staff of the UGA-CRMS and BICY. The efforts of Superintendent John Donahue and BICY personnel are greatly appreciated. 34

36 References Christian, C., Hunters no longer welcome at Big Cypress. Guns & Gear, November: Daerr, E.G., New ORV plan at Big Cypress. National Parks, 74(9-10): 11. Daniel, A., ORVs overrun Big Cypress. National Parks, 73(5-6): A-3. Duever, M.J., J.E. Carlson, J.F. Meeder, L.C. Duever, L.H. Gunderson, L.A. Riopelle, T.R. Alexander, R.L. Meyers and D.P. Spangler, 1986a. The Big Cypress National Preserve. National Audubon Society, New York, New York, 444 p. Duever, M.J., J.E. Carlson and L.A Riopelle, Off-Road Vehicles and their Impacts in the Big Cypress National Preserve. U.S. Department of Interior, National Park Service, South Florida Research Center Report T p. Duever, M.J., L.A. Riopelle and J.M. McCollom, 1986b. Long Term Recovery of Experimental Off-Road Vehicle Impacts and Abandoned Old Trails in the Big Cypress National Preserve, U.S. Department of Interior, National Park Service, South Florida Research Center Report SFRC-86/ p. Hurn, J., Differential GPS Explained. Trimble Navigation, Limited, Sunnyvale, California. 55 p. Staats, E., Draft proposes new access rules for Big Cypress National Preserve. Napes Daily News, Friday, August 13, 1999, Tebeau, C.W., Florida s Last Frontier: The History of Collier County. University of Miami Press, Coral Gables, Florida, 278 p. Welch, R. and M. Madden, Off-Road Vehicle Trail Database for Big Cypress National Preserve. Final Report to the U.S. Dept. of Interior, National Park Service, Cooperative Agreement Number , Center for Remote Sensing and Mapping Science, University of Georgia, Athens, Georgia: 30 p. Welch, R., Madden, M. and R. Doren, Mapping the Everglades, Photogrammetric Engineering and Remote Sensing, 65(2): Welch, R. and M. Remillard, GPS, photogrammetry and GIS for resource mapping applications, In, (Clifford W. Greve, Ed.) Digital Photogrammetry: An Addendum to the Manual of Photogrammetry, American Society for Photogrammetry and Remote Sensing, Bethesda, MD: Welch, R., M. Remillard and R. Doren, GIS database development for South Florida s National Parks and Preserves, Photogrammetric Engineering and Remote Sensing, 61(11):