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11 th International Symposium for GIS and Computer Cartography for Coastal Zones Managementground based LiDAR to assess landslides and coastal cliff erosion (Hobbs et al., 2002; Rowlands et al., 2003;Rosser et al., 2005; Zeibak and Filin, 2007; Oppikofer et al., 2009; Jaboyedoff et al., 2012).Latest efforts at monitoring beaches using terrestrial LiDAR studies as an alternative to airborne LiDAR surveyexposed the potential of this technology to show subaerial beach morphology in detail, benchmarked with high temporalfrequency and low cost (e.g. Nagihara et al., 2004; Gares et al., 2006; Pietro et al., 2008).The use of LiDAR technology for precision measurement on quantifying volumetric changes is a crucial objectivefor understanding the morphology evolution of a beach and dune system environment with highly dynamiccoastal processes that cause sediment exchange alongshore. This allows insight from subaerial beach morphologyvariation to be joined directly to forcing factors of coastal erosion/accretion observations during monitoring surveysthat are capable of acquiring accurate Digital Elevation Models (DEM) at short-term frequencies that are appropriateto high rates of erosion/accretion observed on Ponta Negra beach. The study includes quantification and integratedanalysis of erosion/accretion and even landslides of Morro do Careca dune and correlated foreshore segment that areusually undergoing coastal sediment transportation. Ponta Negra beach surroundings have suffering strong damageto its installed seaside infrastructure due to beach erosion causing socioeconomic conflicts. The proposed DEMcomparison result enables the detection of centimeter-scale variations as well as meter-size changes on beach anddune system on Ponta Negra beach. The relevance of this procedure is because decision makers are planning torebuild damaged infrastructure using a low amount of qualitative and quantitative data related to coastal processes oflong-term and short-term. Consequently, the results intend to subsidize rebuilding plans with an effective methodologythat generate short-term erosion/accretion data background alongshore.MethodsLiDAR quickly creates a surface representation based on a collection of point cloud with coordinates (x, y, z)measured accurately by the laser. The study area was imaged using an ILRIS-3D model (Optech Inc.) tripodmountedscanner able to collect up to 2,000 points per second with a range of up to 2,000 m and generating pointcloud with configurable resolution of up to 1.0 mm in the static method, allowing the beach-dune environment to bemodeled in detail. Two imagery surveys were performed in September 14 th and November 28 th 2012 and for comparisonpurposes both were georeferenced to the same geodetic station network implemented to RN coastal zone(Santos and Amaro, 2011). Table 1 shows geodetic coordinates, ellipsoidal elevation and standard deviation for thecenter points and control targets installed for the surveys and the orthometric height calculated by the systemMAPGEO 2004 (Geoid Model, Brazilian Institute of Geography and Statistics - IBGE) for each month of the study.Table 1. Geodetic coordinates of the center points and control targets, standard deviations and orthometric height obtained usingterrestrial-LiDAR imagery survey on a Ponta Negra Beach sector.SurveyPoint/ N E h sN sE sh HTarget (meter) (meter) (meter) (meter) (meter) (meter) (meter)Point 1 9349201,647 260312,50 -4,475 0,006 0,006 0,016 0,3658September 14 th 2012 Target 1 9349179,231 260334,43 0,217 0,05 0,069 0,100 5,0578Target 2 9349158,06 260272,53 -1,902 0,011 0,009 0,041 2,9388Point 1 9349204 260309,70 -4,772 0,098 0,083 0,031 0,0688November 28 th 2012 Target 1 9349208 260354,30 -2,95 0,098 0,091 0,075 1,8908Target 2 9349156 260269,80 -2,435 0,042 0,051 0,088 2,4058N – North Coordinate; E - East Coordinate; h – ellipsoidal height; sN – standard deviation to North Coordinate; sE –standard deviation to East Coordinate; sh – deviation; H – Orthometric Height.The coordinates have been processed and presented in the reference system WGS84 and UTM projection (SouthZone 25). Therefore, coordinate transportation was executed with L1/L2 Geodetic GPS device (Trimble-5700 model)and processed with the software Topcon Tools. The study area (Morro do Careca and adjacent beach terrace) hasabout 24,000 m 2 , with around 23 to 60 m wide and 500 m long. This section was established based on the edge ofthe shoreline and the partly collapsed boardwalk. The beach morphology and dune face were considered on DEMgeneration and to calculate the sediment volume erosion/accretion between both imagery surveys. The surveys were6
11 th International Symposium for GIS and Computer Cartography for Coastal Zones Managementconducted in spring tide periods that expose the larger foreshore area during low tide (0.2 to 0.3 m high, respectivelyon each survey). The features of interest were the Morro do Careca dune face, backshore and foreshore, besides theinfrastructure deployed. Post processing was done using Polyworks® software tools.ResultsLiDAR surveys were conducted in spring tides that expose larger area of foreshore during low tidal levels. Themorphologic features of interest were the Morro do Careca dune slip face, the most recognizable landmark in Natalcity, and beach foreshore that experienced sedimentary exchange and landforms changes due to coastal processdominated by seasonal fluctuation of waves, tides and winds. Figure 1 presents both DEM to September 14 th (a) andNovember 28 th 2012 (b) acquired with LiDAR for the same beach sector revealing the change in the foreshore altimetryprofile (September 14 th : 2.961 m/ -0.673 m; November 28 th : 4.25 m/ -0.71 m) and emphasizing the decimetricto metric size features along the whole segment. The volume difference between the two surveys for the whole ofthis specific sector of the Ponta Negra beach indicates a positive sedimentary balance of 19,024.13 m 3 .MCMCFigure 1. Digital elevation models for September 14 th (a) and November 28 th 2012 (b) generated from succeeding surveys withLiDAR for a Ponta Negra Beach sector. Arrows highlighting the erosion at the base of Morro do Careca dune (MC) and as wellchannels on beach face caused by runoff of pluvial drainage system.The volumetric difference between DEM of September and November 2012 highlights that between both conditionsoccurred erosion at the base of Morro do Careca dune and deposition of sediments along the foreshore, featuringthis dune system as a relevant continuous source of sediment for the beach. This is the most relevant factor inprotecting the infrastructure installed seaside on this sector of Ponta Negra beach against the harmful effects of theimpact of waves and currents, which also causes sediment deficit in other sectors of the beach. In the same way, the7
Page 1 and 2: CoastGIS Conference 2013: Monitorin
Page 3 and 4: Sponsors
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Page 7 and 8: Santos Basin, BrazilA.F. Romero, R.
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11 th International Symposium for G
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Statistical and spatial toolbox for
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Global oceans and marine planning
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Analysis11 th International Symposi
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Building scenarios and visualizatio
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Using a 3D physics-based visualizat
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Documenting situated tsunami risk p
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SeaSketch11 th International Sympos
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A structured model to enable coasta
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Developing and testing approaches f
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A dynamic GIS as an efficient tool
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GIS spatio-temporal modeling of hum
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ResultsCollected data11 th Internat
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The use of GIS and geospatial techn
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Ocean Radar for Monitoring of the C
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Geophysical investigations of marin
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A semi-supervised learning framewor
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Simulation of maritime paths taking
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COINAtlantic: Sharing through open
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Implementation of the marine data i
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Perspectives11 th International Sym
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References11 th International Sympo
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Conclusion11 th International Sympo
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Tools and best practices for coasta
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Washington Coastal Atlas: creating
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Methods11 th International Symposiu
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Methods11 th International Symposiu
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Acknowledgments11 th International
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Long-term continuous observations o
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Comparing endmember extraction meth
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Integration of scientific data as a
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Conclusions11 th International Symp
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