Evaluation of the efficiency of dune reconstruction techniques in Xangri-lá (Rio Grande do Sul, Brazil)

•Evaluation of the efficiency of dune reconstruction.•Stormwater runoff piping under the frontal crest of the dune diminished its instability.•The spreading of inert vegetable material accelerated the recolonization of the dune.•Adaptation of the dunes recuperation projects in function of the system responses.

The effects arising from the inordinate use of the coastal zone are unfolding in a reduction or even elimination of the foredune systems. Therefore, rehabilitation programs of these systems are currently one of the priorities of the coastal managers. The proposal of this study is to assest the efficiency of the recuperation techniques of the foredune system, having as a starting point the performance of a stormwater runoff piping installation. The first stage of this work evaluated the methods utilized for the dune system recuperation through digital terrain models and the sediment volume variations in three distinct periods, discussing the unanticipated alterations due to the interventions performed. The second part established a correlation between the actual accumulation of sediments and the calculation of the potential aeolian sand transport, with the aim of choosing the empirical equation that best fits the aeolian sand transport in the Rio Grande do Sul State coast. The results obtained show the efficiency of Northeast and East-Northeast winds in the transport of sediments towards the foredunes, resulting, thus, in success in the dunes reconstruction. The alterations in the system by the interventions realized evidence the necessity for constant adaptation of the dunes recuperation project in function of the system responses. The equation of Bagnold (1941) is the most accurated to predict the potential aeolian sand transport to the study area.