An open-source QGIS plugin to support hydrological and watershed management planning in mountain basins

In recent decades, watershed management has assumed a pivotal role in the face of the progressive anthropization of land use and the increasing frequency of extreme hydro-geomorphic events caused by climate change. Indeed, the reduction of hydro-geological risk in mountain basins is contingent on the effective and sustainable design of torrent control structures, including check dams and bed sills.

The up-to-date knowledge of basin morphology and the comprehension of the interaction between torrent control works and hydro-geomorphological phenomena represent fundamental elements for designing, managing and maintaining mountain watersheds. Nowadays, the interpretation of basin processes is significantly enhanced using accurate, high-resolution remote sensing (RS) data, in conjunction with analyses employing GIS software. However, the use of such techniques is not yet widespread and there is a need for user-friendly tools to facilitate the effective processing of RS data to support planning and management activities.

To address these demands, this work proposes the development of a QGIS plugin (i-GIS4HydroPlan) to fully support the hydrological design of torrent control structures, implementing functions such as the automatic extraction of watershed boundaries from the Digital Terrain Model (DTM), the calculation of the flow directions, upslope contributing areas, routing, and, finally, the design hydrograph. This output is estimated through the Kinematic Local Excess Model (KLEM), an event-based model applicable to small mountain basins that combines the equations of the Soil Conservation Service for the calculation of the effective rainfall, the kinematic method for the flow propagation to the outlet and a linear reservoir for the simulation of base flow. Moreover, the plugin incorporates functionalities that facilitate the management of multi-temporal DTMs, thereby enabling a comprehensive analysis of sediment dynamics within the entire basin or single torrent reaches equipped with torrent control structures. The module encompasses algorithms for the co-registration of DTMs and the error analysis that affects the DTM of Difference (DoD).

The plugin will be distributed under an open-source license with the objective of enhancing its dissemination and facilitating the standardization of workflows. This will in turn allow a more efficient design of new torrent control works and the assessment of existing structures to determine their criticality and establish maintenance priorities.

Acknowledgement: This study was funded by the European Union - NextGenerationEU, in the framework of the consortium iNEST - Interconnected Nord-Est Innovation Ecosystem (PNRR, Missione 4, Componente 2, Investimento 1.5, D.D. 1058 23/06/2022, ECS00000043 – Spoke1, RT1B, CUP G23C22001130006). The views and opinions expressed are solely those of the authors and do not necessarily reflect those of the European Union, nor can the European Union be held responsible for them.