Histórico de antropização e supressão das dunas no balneário Hermenegildo, Rio Grande do Sul, Brasil (History of anthropization and dune suppression in Hermenegildo coastal settlement, Rio Grande do Sul, Brazil)

Diversas alteracoes ambientais tem sido observadas no Planeta, produto de mudancas climaticas globais, crescimento demografico, rapidas alteracoes no uso da terra e demais processos inter-relacionados, sendo uma das mais marcantes as alteracoes impostas as dunas costeiras. Este trabalho visa realizar um historico de antropizacao e sua influencia na supressao dunar no balneario Hermenegildo, situado no extremo sul do Brasil. Para isto foram realizadas entrevistas com historiadores e moradores antigos do local; analisadas fotografias aereas de 1947 e 1964, fotografias convencionais da area urbana e orla ate o inicio dos anos 2000, imagens orbitais disponiveis no software Google Earth PRO de 2005 e 2016, mosaicos da orla obtidos a partir da face da praia uma vez ao ano entre 2009 e 2016 e dois mosaicos de fotografias aereas verticais e obliquas in loco utilizando um drone DJI Phantom 3 em 2016. Os primeiros assentamentos ocorreram ha mais de um seculo, periodo em que as dunas prevaleciam no local. Por volta da decada de 1960 especies exoticas comecaram a ser plantadas com objetivo de diminuir o transporte eolico de sedimentos e possibilitar a urbanizacao. As dunas frontais, as ultimas remanescentes na area urbana, estao sendo suprimidas entre a praia e as edificacoes/contencoes em funcao do processo de erosao costeira. O historico do local remete a mudancas climaticas e ambientais locais com estabilizacao do solo, substituindo-se dunas moveis por vegetacao exotica, urbanizacao, aterros e estruturas de contencao a erosao costeira. Several environmental changes have been observed on the planet, a product of global climate change, demographic growth, rapid changes in land use and other inter-related processes, one of the most striking of the changes imposed on the coastal dunes. This study aims at describing a brief history of anthropization process and its influence on dune suppression in Hermenegildo, a coastal settlement located in the extreme south of Brazil. Besides, the following were analyzed: aerial photographs taken from 1947 to 1964; conventional photographs of the urban area and the seashore up to the 2000’s; orbital images available at the software Google Earth PRO ® from 2005 and 2016; annual mosaics of the seashore got from the beach face, from 2009 to 2016; and two mosaics of vertical and oblique aerial photographs taken in loco by a drone in 2016. The first settlements took place more than a century ago, in a period in which mobile dunes prevailed in that area. Around the 1960’s, exotic species started to be planted so as to decrease eolian sediment transport and enable urbanization, making the former field of mobile dunes into fixed and vegetated dunes. Frontal dunes, the last to remain in the urban area, have been suppressed between the beach and the buildings/retaining walls as the result of the coastal erosion process.  The history of the place refers to local environmental changes with soil stabilization, since mobile dunes were replaced by exotic vegetation, urbanization, levees and retaining walls in order to mitigate coastal erosion. Keywords: Environmental changes, human activity, coastal erosion