Terraced Landscapes as NBSs for Geo-Hydrological Hazard Mitigation: Towards a Methodology for Debris and Soil Volume Estimations through a LiDAR Survey

Terraced landscapes are widely applied in many mountainous regions around the world
as a result of the necessity to practice subsistence agriculture. Hence, they can be regarded as one of
the most diffused anthropogenic modifications of the Earth’s surface. Different techniques have
been used for their implementation leading to the artificial immobilization of debris and soil along
the slopes whose surface is interrupted by a sequence of sub-horizontal and sub-vertical areas often
using stone walls. In some areas of the world, such interventions are thousands of years old and
their resistance to the degradation caused by the morphogenetic system can be attributed to the
permeability of the stone walls as well as to their regular maintenance. In some other areas, the lack
of maintenance has been the main cause for degradation processes ending with their collapse. The
effects of climate change manifested through higher intensities and higher frequencies of rainfall
are likely to accelerate the degradation process further by causing terraces to act as a source of debris
or hyperconcentrated flow. This will in turn increase the severity of geo-hydrological hazards. The
measures concerning reduction of geo-hydrological hazards caused by are sought through
identification of abandoned terraces and assessment of the potential for their sudden collapse. The
present paper describes a framework for identification of abandoned terraces and estimation of the
potential volume of shallow landslides that can be generated. The research conducted aims to
advance the existing hazard assessment practices by combining numerical modeling with
processing of high-resolution LiDAR data. A new algorithm is developed to support localization of
terraces. The catchment scale approach applied to eight smaller catchments enables estimation of
the total volume of soil and debris trapped along the slopes. It also generated some important
quantitative data which will be used in the future risk assessment work. The work has been carried
out within the EU-funded H2020 project RECONECT.