MONITORING SHORELINE AND BEACH MORPHOLOGIC CHANGE AT KENNEDY SPACE CENTER, CAPE CANAVERAL, FLORIDA

Transcription

1 MONITORING SHORELINE AND BEACH MORPHOLOGIC CHANGE AT KENNEDY SPACE CENTER, CAPE CANAVERAL, FLORIDA Annual Report Phase 3, Oct Sept Dr. Peter N. Adams Dr. John Jaeger Dr. Richard MacKenzie Shaun Kline Department of Geological Sciences 241 Williamson Hall P.O. Box University of Florida Gainesville FL

2 Table of Contents Table of Contents... 2 Executive Summary... 3 Introduction... 4 Methods... 4 Field Surveys of Topographic Change... 4 Topographic Data Processing... 5 Observations During Reporting Period... 6 Wave Climate... 6 Shoreline Variability... 6 Discussion and Conclusions... 7 Figures... 9 Literature Cited

3 Executive Summary This report provides an update on progress for the period 1-Oct-2011 through 30-Sep-2012, as required by contract #98217 between the University of Florida (UF) and Innovative Health Applications (IHA), the environmental contractor for the National Aeronautics and Space Administration (NASA). The contract represents a two-year continuation of the KSC Dune Vulnerability Study, which was initiated in May Findings from work conducted prior to October 2011 can be found in previous annual reports (Jaeger et al., 2010; Jaeger et al., 2011). A presidential initiative has been proposed to improve, expand, and modernize the Kennedy Space Center (KSC) infrastructure. Even with the modernization efforts, launch operational imperatives will keep much of that infrastructure within 500 m of the Atlantic Ocean coastline. Shoreline retreat near existing critical infrastructure threatens these facilities as well as critical endangered-species habitat along several kilometers of the Cape Canaveral shoreline. The causative factors for the spatial patterns of accretion and erosion observed at KSC have not been identified, but are likely due to sea level rise and interaction of the offshore wave energy with the unique shoal bathymetry and the underlying geologic framework. To better understand the evolving geomorphology and patterns of shoreline accretion and retreat along the Cape Canaveral coast, UF researchers, in collaboration with the United States Geological Survey (USGS), established a monitoring project at the NASA-KSC site. The project uses real time kinematic (RTK) differential GPS (GPS), remote sensing, wave monitoring and modeling, fixed camera observations, and sediment analyses. UF has been collecting high spatial density RTK-GPS data since May 2009, resulting in 55 surveys to date. During the current reporting period (1-Oct-2011 through 30-Sept-2012), 15 RTK-GPS surveys were conducted, and as of the assembly of this report, date from 13 of the surveys had been qualitycontrolled, and analyzed. During the reporting period, offshore wave conditions were similar to those typically witnessed over an annual cycle. The winter of was characterized by regular (weekly) nor easter storms providing waves from northerly then easterly directions. Late spring and early summer 2012 were highlighted by two tropical storms (Beryl and Debbie), but neither produced exceptional wave conditions. During the reporting period, shoreline position showed moderate net advance during the reporting period. The shoreline change envelope, which is a measure of total shoreline variability over the study reach, was slightly higher (Mean ~ 13.5 meters) than in the previous two years of observations. Over the 40-month study period, the 4 (alongshore) regions of the NASA-KSC beach display demarcation based on beach width, as measured from the dune crest to the position of the mean high water shoreline position. Beach width variability is greatest at the north end of False Cape, where the historical trend in shoreline position transitions from decadal narrowing (to the north) to decadal widening (to the south). In each of the 4 regions, a seasonal signal in shoreline position (beach width) is evident, characterized by beach widening from late spring to early fall and abrupt retreat during winter nor easter season. 3

4 Introduction The effects of climate change on sea level and ocean wave conditions will produce changes in spatial and temporal patterns of nearshore water levels and sediment transport, resulting in morphologic adjustment of beach and dune systems. Recent geomorphic changes within the coastal zone at Kennedy Space Center (KSC), Cape Canaveral, Florida, are threatening NASA infrastructure and have altered endangered wildlife habitat. Because of the lack of previous coastal information at this site, there is a critical need to provide a baseline understanding of the coupled beach-dune response to the wave climate. Since 2008, the U.S. Geologic Survey (USGS) has been conducting a dune vulnerability study to provide a decision support system for the environmental management team at NASA-KSC. A major component of this project requires observations of shoreline and beach morphologic variability in order to assess current risk and to help predict and evaluate future risk. In support of the USGS study, and to better understand the coastal geomorphology and patterns of shoreline accretion and retreat along the Cape Canaveral coast, a project was initiated by the University of Florida (UF), using real time kinematic (RTK) differential Global Positioning System (GPS) surveys to monitor beach topographic change. Initially, UF conducted a 12- month pilot study of topographic monitoring from May 2009 April The findings from that work are summarized in the Annual Report for Phase 1 (Jaeger et al., 2010). After the pilot study, UF was contracted for an additional year of observations, which expanded the effort to include remote sensing, wave monitoring and modeling, fixed camera observations, and sediment analyses in addition to the ongoing RTK-GPS topographic monitoring. The findings from that work are summarized in the Annual Report for Phase 2 (Jaeger et al., 2011). Most recently, UF was awarded an additional two-year contract to continue only the RTK-GPS surveys to monitor beach topographic change. This report provides results from the most recent year of observations (Oct. 1, 2011 Sept. 30, 2012), the first year of the current contract. Herein, we (1) briefly describe the methods used to monitor beach topographic change, (2) present the locations of mean high water (MHW) shorelines derived from the topographic data collected during 13 (of the 15) surveys spanning the interval from Oct. 1, 2011 through Sept. 30, 2012, (3) conduct a shoreline change analysis for the observation interval, and (4) summarize shoreline patterns during the entire (40-month) observation period to date. Methods Field Surveys of Topographic Change Monthly beach surveys were conducted with Trimble model 5800 RTK-GPS equipment along the ~10-km reach of NASA-KSC coastal property (Figure 1). The GPS base station was set on one of several National Geodetic Survey markers (referred to as WARD and BUDROE ) located on the television camera pads along Phillips Parkway (Figure 1). Two RTK-GPS rover antenna units were mounted 2.25 m apart on a trailer towed by an all-terrain vehicle. This allowed for data collection along two parallel transverse tracks covering the length of the shoreline along the study area with each rover antenna set to collect a data point every 1.5 m. 4

5 Horizontal and vertical datums and projections for each type of data are shown in Table 1. To construct a 3-D surface model of the beach morphology, along-shore transects were acquired during low tide at the lowest elevation allowable due to beach conditions and at the highest beach elevation allowed by U. S. Fish and Wildlife Service and NASA environmental constraints. Additional elevation data were collected between these bounding transects along all slope breaks (e.g., berm). Figure 2 shows the data collection density of a typical survey, with each green dot representing a single RTK-GPS point measured by a collector, and the two parallel lines represent the two rover antennas, demonstrating the number of passes required to reproduce beach morphology. Up to six along-shore transects (12 total track lines) were collected in each survey. Table 1. Datum and projection information for different data types. Data Type Hor. Datum Vert. Datum Projection Raw GPS NAD 83 NAVD 88 Mollweide GPS projected into GIS NAD 83 NAVD 88 UTM All GIS Files NAD 83 NADV 88 UTM Table 2. Dates of RTK-GPS field surveys, total numbers of data points collected, numbers of data points used (and percentages) after quality control procedures which removed points showing instrument error greater than 5 cm and 10 cm. Survey Date Data Points Collected Data Points Used (5 cm) % Data Lost at QA/QC (5 cm) Data Points Used (10 cm) % Data Lost at QA/QC (10 cm) File Name in Master_Survey_QC_Files Oct. 11, ,140 52, , CpCnv_111011_Bch_(Type) Oct. 15, ,650 60, , CpCnv_111015_Bch_(Type) Nov. 10, ,314 42, , CpCnv_111110_Bch_(Type) Dec. 15, ,976 57, , CpCnv_111215_Bch_(Type) Jan. 07, ,705 58, , CpCnv_120107_Bch_(Type) Feb. 10, ,013 60, , CpCnv_120210_Bch_(Type) Feb. 21, ,990 42, , CpCnv_120221_Bch_(Type) Mar. 8, ,081 57, , CpCnv_120308_Bch_(Type) April 7, ,321 41, , CpCnv_120308_Bch_(Type) May 5, ,830 86, , CpCnv_120505_Bch_(Type) June 3, ,404 66, , CpCnv_120603_Bch_(Type) July 3, ,276 46, ,269 0 CpCnv_120703_Bch_(Type) Aug. 4, ,145 55, , CpCnv_120804_Bch_(Type) Aug. 30, ,382 66, , CpCnv_120830_Bch_(Type) Sept. 27, ,480 71, , CpCnv_120927_Bch_(Type) Topographic Data Processing The point elevation data were offloaded and processed with Trimble Business software, and all data with an instrument error greater than 10 cm (then again for 5 cm) in either the vertical or horizontal were discarded. Table 2 shows dates of surveys, total number of data points collected for each survey, the number of data points used in generating the digital elevation model, percentage of the measurements that had an instrument error over 5 cm and 10 cm, respectively, and the name of the corresponding Microsoft Excel file containing the survey data. Survey 5

6 elevation points were imported to an ArcGIS software platform and a bounding polygon was derived for each survey. The elevation points and bounding polygon were put into a common projection (Table 1) and converted to a 3-dimensional Triangular Irregular Network (TIN) to reproduce beach morphology (Figure 2). The TIN was converted to a one-meter resolution raster. A single contour was extracted at the mean high water (MHW) mark, which was set by the USGS at 0.28 m NAVD88 elevation for the Cape Canaveral coast. Using the defined MHW shorelines, we are able to track erosional and depositional patterns as they evolve from one survey to the next. Observations During Reporting Period Wave Climate For the current reporting period of 1-Oct through 30-Sept. 2012, we compiled wave climate observations, including significant wave height (H S ), dominant wave period (T D ), and wave direction, from three National Oceanic and Atmospheric Administration (NOAA) National Data Buoy Center instruments: 1) Buoy 41009, located 20 nautical miles east of Cape Canaveral (H S and T D only), 2) Buoy 41010, located 120 nautical miles east of Cape Canaveral (H S and T D only), and 3) Buoy 41012, located 40 nautical miles east-northeast of St. Augustine, serving as a directional wave proxy. Figure 3 shows the wave climate throughout the study period (10/01/2011 to 10/01/2012). The winter months of registered typical patterns of Nor Easter storms, in which wave directions migrate from north-northeasterly to easterly orientations over 3-7 day intervals. The summer months of 2012 registered typical quiescent offshore wave conditions, including significant wave heights not in excess of 2 m, and dominantly easterly orientations. No extraordinary events (e.g. hurricane landfalls) occurred during this period, but other notable events are highlighted according to the classification scheme of Dolan and Davis (1992). They include: 1. Early season Class II Nor Easter October 6-12, 2011, which produced maximum offshore significant wave heights in excess of 8 meters. Results from the WaveWatch 3 hindcast for this event are shown in Figure Tropical Storm Beryl (05/23/2012 to 05/30/2012) that made landfall in Jacksonville Beach, Florida after organizing along Florida s east coast. 3. Tropical Storm Debby (06/23/2012 to 06/27/2012) that crossed north-central Florida before dissipating in the Atlantic Ocean. The ENSO index began slightly negative (-0.968) at the beginning of the study, but these conditions weakened in March The remainder of the study period was characterized by a slightly positive ENSO index, as La Nina conditions transitioned into a weak El Nino event. Shoreline Variability For the current reporting period of 1-Oct through 30-Sept. 2012, we provide lunarmonthly shoreline positions (as maps and time series plots) at four representative sites within the 6

7 study area, as well as the alongshore distribution of the annual shoreline change envelope (SCE) calculated from 13 (of 15) RTK-GPS topographic surveys. Figure 5 provides positions of the MWH datum based shoreline within 4 regions of the study area for 13 (of 15) survey dates during the reporting interval. Region 1 exhibits moderate net shoreline advance (Figure 6) and a mean shoreline change envelope (SCE) of approximately 12 meters (Figure 7). Region 2 exhibits no significant net shoreline advance, nor retreat (Figure 6), and a mean SCE of approximately 14 meters (Figure 7). Region 3 exhibits pronounced net shoreline advance (Figure 6) and a highly spatially variable SCE with a mean value of approximately 20 meters (Figure 7). Region 4 exhibits moderate net shoreline advance (Figure 6) and a mean SCE of approximately 10 meters (Figure 7). Discussion and Conclusions In this report we have focused on the survey data collected during period, which comprise the most recent 12 months of the our total (40 month-long) observation period. In this section we present the complete record of shoreline position during the 40-month period from May 2009 through August 2012 and comment on the documented morphologic behavior. In order to place the observations in context of the long term study at the NASA-KSC site (May 2009 to present), compilation diagrams showing annual positions of the MWH datum based shoreline and alongshore distribution of net annual change in MHW shoreline position, are provided as Figures 8 and 9, respectively. Of particular interest, in Figure 9, is the behavior of annual reversals, to borrow from the concept of storm reversals presented by List et al. (2006). The annual snapshots of shoreline positions, representative of each region, mask the richness of morphologic behavior available from the 50+ surveys acquired during the 40-month study period. To further explore the monthly variability and seasonality of shoreline position, we present a pseudocolor time series plot in Figure 10. Highlights of the shoreline position behavior include: 1. The left (main) panel of Figure 10 shows, foremost, that the defined regions (1-4) in our study correspond, in general, to beach width and beach width variability. Region 1 (0-2.1 km alongshore, DSAS transects #1-210) is characterized by a temporally stable (s.d. < 4 m) beach of intermediate width (mean = m). Region 2 ( km alongshore, DSAS transects # ) is characterized by a temporally variable (s.d. < 4 m), narrow (mean = m) beach that exhibits a fair amount of alongshore variability, as well. For example, between km alongshore (DSAS transects # ), the beach is narrow and stays narrow year round, whereas between 4-5 km alongshore (DSAS transects # ), the beach narrows during the winter and widens during the summer. Region 3 ( km alongshore, DSAS transect # ), the area surrounding and including False Cape, shows the widest beaches in the study region (mean > 50 m, in places) and the highest temporal variability (s.d. > 8 m) around DSAS transect # Region 4 ( km alongshore, DSAS transect # ) can be defined as a narrow, temporally stable beach (mean = 30 m, s.d. < 4m). 7

8 2. Beach width variability over the 40-month period is greatest at the north end of False Cape, where the historical trend in shoreline position transitions from decadal narrowing (to the north) to decadal widening (to the south). 3. In each of the 4 regions, a seasonal signal in shoreline position (beach width) is evident, characterized by beach widening from late spring to early fall and abrupt shoreline retreat following certain tropical storms (e.g., Irene in August 2011) or during winter nor easter season (Oct.-Feb) of each year. 4. Winter nor easters are major agents of shoreline retreat, but vary in intensity interannually. The winter of had notable shoreline retreat along the entire study area, where the winter of had less retreat, with the winter of intermediate between these two. 8

9 Figures Figure 1. Annotated satellite image map of NASA-KSC study area. Identified with white labels are three launch complexes (LC-39A, LC-39B, and LC-41). Turquoise markers denote locations of NGS monuments, where the base stations were routinely set up for RTK-GPS surveys. Select DSAS transects are shown in red. Positions of UF reference sampling transects are shown in yellow. 9

10 Figure 2. Representative RTK-GPS survey collection density, TIN of collected points, and MHW shoreline at 0.28 m contour. 10

11 Figure 3. Deep-water wave height, period, and direction recorded at NOAA Buoy 41009, 41010, and Arrows identify timing of notable meteorological events. Magenta lines identify dates of RTK-GPS surveys. 11

12 Figure 4. WaveWatch III numerical model hindcast output showing the distribution of wave heights during the Nor Easter of early October

13 ¹ Region 1 Kilometer 33 UF Transect 10 Region 2 Kilometer 31 UF Transect 35 UF Transect Profile Shoreline Dates 10/11/ /15/ /10/ /15/2011 1/7/2012 2/10/2012 2/21/2012 3/8/2012 4/7/2012 5/5/2012 6/3/2012 7/3/2012 8/4/2012 UTM 17N (m) NAD 83 NAVD 88 (m) University of Florida Geological Sciences 2012 Region 3 Kilometer 26 UF Transect 105 MHW 0.28 m Datum Based Shorelines (Oct Aug. 2012) Region 4 Kilometer 24 UF Transect (m) Figure 5. Positions of the MWH datum based shoreline within 4 regions of the study area for 13 (of 15) survey dates during the reporting interval. 13

14 60 55 Region 1: DSAS Transect 80 Region 2: DSAS Transect 280 Region 3: DSAS Transect 765 Region 4: DSAS Transect Shoreline Position (m) Oct Jan Apr Jul Oct 2012 Figure 6. Time series plots of the MHW shoreline positions within 4 regions of the study area for 13 (of 15) survey dates during the reporting interval. 14

15 Figure 7. Alongshore distribution of annual shoreline change envelope. 15

16 ¹ Region 1 Kilometer 33 UF Transect 10 Region 2 Kilometer 31 UF Transect 35 Region 3 Kilometer 26 UF Transect 105 Region 4 Kilometer 24 UF Transect 120 UF Transect Profile Shoreline Dates 5/6/2009 5/2/2010 5/19/2011 5/5/2012 UTM 17N (m) NAD 83 NAVD 88 (m) UF Geological Sciences 2012 MHW 0.28 m Datum Based Shorelines (May 2009, May 2010, May 2011 and May 2012) (m) Figure 8. Annual positions of the MWH datum based shoreline within 4 regions of the study area over entire observation interval (May 2009 to present). 16

17 Figure 9. Alongshore distribution of net annual change in MHW shoreline position. 17

18 Figure 10. Psuedocolor time series plot showing alongshore distribution MHW shoreline position (with respect to surveyed dune crest) history during 40-month observation period from May 2009-August Colorbar values are in units of meters. Right panels show mean and standard deviation of shoreline position over the entire KSC coastal reach for the 40-month period. 18

19 Literature Cited Dolan, R., and Davis, R. E. (1992). An Intensity Scale for Atlantic Coast Northeast Storms. Journal of Coastal Research, 8(4), Jaeger, J. M., Adams, P. N., and MacKenzie, R. A. (2010). Establishing measures and proxies of shoreline change at Cape Canaveral, Florida: Annual Report Phase 1, May 2009-May 2010 (pp. 1 91). Gainesville, FL: NASA-IHA Annual Report. Jaeger, J. M., Adams, P. N., MacKenzie, R. A., Kline, S., Maibauer, B., Lesnek, A., Harris- Parks, E., and Lovering, J. L. (2011). Monitoring Shoreline And Beach Morphologic Change At Kennedy Space Center, Cape Canaveral, Florida: Annual Report Phase 2, May 2009-May 2011 (pp ). Gainesville, FL: NASA-IHA Annual Report. List, J., Farris, A., and Sullivan, C. (2006). Reversing storm hotspots on sandy beaches: Spatial and temporal characteristics. Marine Geology, 226,