New Technologies to Assess and Map an Urban Riparian Area in Drama, Greece, and Determine Opportunity Sites for Litter Traps

Riparian areas offer many ecosystem services, especially in urban settings. Their conservation can be complex because of the many urban anthropogenic pressures they face. Adopting new technological approaches can provide insights on the most cost-effective and sustainable management for riparian areas. In this study, different new technological approaches were implemented to assess and map environmental variables and find the optimal location of nature-based solutions (e.g., litter traps). The study area was Agia Varvara Park in Drama, Greece, a unique natural urban riparian area. The approaches utilized were categorized as aerial, terrestrial, and surface/underwater. Specifically, these approaches included unmanned aerial vehicles that incorporated high-resolution regular and thermal cameras to capture the surface environmental conditions and unmanned underwater vehicles to capture the underwater environmental conditions. The produced orthomosaics and digital surface models enabled us to estimate the boundaries of the water surface in Agia Varvara Park. A GPS tracker was also used to record the potential movement route of litter. Finally, a sonar device was utilized to estimate the water depth of potential cross-sections of Agia Varvara’s stream where the litter trap could be installed. The above datasets were used to develop spatial datasets and accompanying maps that were utilized to find the optimal opportunity sites for the litter trap. A litter trap is a floating device that gathers and maintains litter, vegetation, and other debris. Two specific locations were proposed based on water presence, water depth, channel’s width, limited vegetation for accessibility, wildlife existence, litter’s water route, and stopping location time. Such traps enable the collection of anthropogenic litter. In one location, a litter trap has been installed and is being tested. Overall, the above approaches could be used to suggest other nature-based solutions and/or their optimal location, thus enhancing the sustainable management of urban riparian areas.