Preliminary study of Fella and But watersheds: how to exploit databases of channel control structures and High-Resolution Topography (HRT)

The study of sediment dynamics and its interaction with channel control structures enables the application of the most suitable mitigation measures for hydrological risk. An updated inventory of channel control structures is one of the most important types of information for the monitoring and planning of old and new prevention works. Also consulting historical data and maps can help to understand the evolution of catchment dynamics and the set-up of hydraulic control structures. Nowadays, new monitoring techniques can be leveraged, facilitating frequent and relatively low-cost surveys and ensuring timely interventions. High-resolution topography data (HRT) such as Light Detection and Ranging (LiDAR) are essential for accurately identifying and mapping watershed characteristics. Through HRT, updated Digital Terrain Models (DTMs) can be derived, facilitating multi-temporal analysis. This analysis, known as DTMs of Difference (DoD), involves comparing two DTMs to qualitatively and quantitatively assess erosion and deposition patterns through time. A critical preliminary step, often necessary for conducting reliable multi-temporal analysis, is data co-registration. The main aim of this study is to update the regional channel control works inventory, add other useful information as a base for subsequent catchment dynamic studies and analyse the HRT data available. This contribution presents preliminary results of the historical analysis of geomorphic changes, updating the inventory of channel control structures and co-registration of two HRT DTMs in two large catchments in Friuli Venezia-Giulia (Italy): But and Fella basins (324 Km2 and 703 Km2, respectively). Initially, historical topographic maps were consulted to analyse the evolution related to the morphologic changes and the location of old check dams. Additionally, the channel control structures regional database was analysed to study its accuracy, considering the check dams location, and the data available for each (e.g., year of construction, materials, height, length, thickness, conservation state). Finally, the co-registration process of LiDAR data was evaluated to realize reliable DoD analysis. In conclusion, based on these preliminary results, our study provides a workflow to update a regional channel control structures inventory and to pre-process HRT data, preparing robust topographic inputs for a subsequent multi temporal analysis of the catchment dynamic.