Variability of the beach-dunes system for the north coast of Rio Grande do Sul (Palmares do Sul to Torres, Brazil) supported by Light Detection And Ranging – Lidar

Abstract

Morphometric and geological parameters such as coastline orientation, wind drif potential, subaerial beach slope and width and mean grain size are crucial to the geomorphology of the beach-dune system. Surveys on the northern coast of the Rio Grande do Sul (RS) through the laser scanner system provided major morphometric parameters quickly and accurately without the need for in situ surveys. The lateral variability of these parameters and their association with geological features were analyzed through cluster analysis and multidimensional scaling for the beach sectors along 123 km between the balnearies of Palmares do Sul and Torres defining four affinity groups. The variables that contributed most to the differentiation of the groups were: width of the subaerial beach, wind drift potential, coastline azimuth and percentage of medium sand. Groups 1 and 4, located further south of the study area, have beaches with wider sub aerial beach profiles, wind drift potential, volume change above the datum, and have the lowest azimuths of the shoreline. Group 1 displays the highest volume and height of the foredunes. The lower volume of the foredunes are associated to group 3, which displays the higher azimuth of the shoreline implying in a almost parallel wind to the coastline which reflect in a low wind drift potential. Group 2 shows values of subaerial beach width similar to group 3, but displays a greater foredune volume and height being these differences explained by its lower coastline azimuth. The variables width of the subaerial beach, wind drift potential and coastline azimuth associated with the beach mean grain size are important factors to explain the variability of the foredunes along the northern coast of the RS.