HYDRO-MORPHIC ANALYSIS OF URBAN BASINS CHANGES AND HYDROLOGICAL RESPONSE ASSESSMENT: THE CASE STUDY OF THE CITY OF MATERA LETTURA IDRO-MORFICA DELLE TRASFORMAZIONI OPERATE NEI BACINI URBANI E VALUTAZIONE DELLA RISPOSTA IDROLOGICA: IL CASO STUDIO DELLA CITTÀ DI MATERA

The evolution of cities is important for tracing a hydrological vision of the territories and their sustainability as urban morphologies and uses regulate the rainfall-runoff processes. The analysis of water fluxes in urban areas under different conditions assess the hydrological response, the hydro-morphic features and their interrelation with urban, architectural or administrative characteristics. This study presents an approach for hydro-morphic analysis of urban basins changes and hydrological response assessment applied to the city of Matera (Italy). Matera - especially the Sassi - represents an ideal case study: in its history it evolved as a complex urban ecosystem of dwellings and water infrastructures for collection, storage, and drainage, whereas in recent years the city transformation led to frequent urban pluvial flood events. The study adopted for hydrodynamic simulations different two-dimensional models: an adapted version of FLORA-2D and LISFLOOD-FP with three numerical schemes (Acceleration, Flow-Limited and Roe). The study included the estimation of hydraulic hazard for extreme precipitation in urban areas with the FLORA-2D model, the evaluation and the comparison of the characteristics and performance of the hydrodynamic models. FLORA-2D results were consistent with flood events observations. LISFLOOD-FP with the Acceleration scheme provided results similar to FLORA-2D and required shorter simulation times. The LISFLOOD-FP schemes tended to converge with FLORA-2D with greater depth tolerance thresholds, so they can offer useful alternatives for some cases. For large areas, the Flow-Limited scheme could be preferred because of its reduced computational times. FLORA-2D appears the most suitable for planning purposes as it allows permeability spatial variations by using differentiated effective rainfall hyetograph whereas LISFLOOD-FP input hyetograph can variate only over time. The choice of simulation model will depend on the characteristics of the study (purposes, area of interest, data available, desired computational time). In light of this, FLORA-2D was used to evaluate the hydrological response thus the hydrological impacts of urban basin changes by calculating the hydraulic invariance index. The analysis of two urbanisation scenarios (1954 and 2019) allowed to identify the urban areas more prone to flooding phenomena, coinciding with road network and downstream areas. The proposed methodology can be used effectively to read the urban areas and interpret their evolution to protect the territories from water-related risks and to increase sustainability of built environment development, evaluating the hydrological impacts of past or future interventions.