Surface Water Flow Balance of a River Basin Using a Shallow Water Approach and GPU Parallel Computing—Pescara River (Italy) as Test Case

Antonio Pasculli,Carmine Di Nucci,Nicola Sciarra,Roberto Longo

doi:10.3390/w14020234

Antonio Pasculli, Carmine Di Nucci + Show 2 more

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https://doi.org/10.3390/w14020234

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Abstract

The analysis and prevention of hydrogeological risks plays a very important role and, currently, much attention is paid to advanced numerical models that correspond more to physical reality and whose aim is to reproduce complex environmental phenomena even for long times and on large spatial scales. Within this context, the feasibility of performing an effective balance of surface water flow relating to several months was explored, based on accurate hydraulic and mathematical-numerical models applied to a system at the scale of a hydrographic basin. To pursue this target, a 2D Riemann–Godunov shallow-water approach, solved in parallel on a graphical processing unit (GPU), able to drastically reduce calculation time, and implemented into the RiverFlow2D code (2017 version), was selected. Infiltration and evapotranspiration were included but in a simplified way, in order to face the calibration and validation simulations and because, despite the parallel approach, it is very demanding even for the computer time requirement. As a test case the Pescara river basin, located in Abruzzo, Central Italy, covering an area of 813 km2 and well representative of a typical medium-sized basin, was selected. The topography was described by a 10 × 10 m digital terrain model (DTM), covered by about 1,700,000 triangular elements, equipped with 11 rain gauges, distributed over the entire area, with some hydrometers and some fluviometric stations. Calibration, and validation were performed considering the flow data measured at a station located in close proximity to the mouth of the river. The comparison between the numerical and measured data, and also from a statistical point of view, was quite satisfactory. A further important outcome was the capability to highlight any differences between the numerical flow-rate balance carried out on the basis of the contributions of all known sources and the values actually measured. This characteristic of the applied modeling allows better calibration and verification not only of the effectiveness of much more simplified approaches, but also the entire network of measurement stations and could suggest the need for a more in-depth exploration of the territory in question. It would also enable the eventual identification of further hidden supplies of water inventory from underground sources and, accordingly, to enlarge the hydrographic and hydrogeological border of the basin under study. Moreover, the parallel computing platform would also allow the development of effective early warning systems, for example, of floods.

Highlights

The appropriate selection of an effective calculation tool constitutes the first action to be explored and pursued in order to obtain, as far as possible, a correct forecast of the evolution of possible impacting natural phenomena for the territory under observation
The smoothed particle hydrodynamics (SPH) method appears to be quite well established [6–8].The mistaken was that Reduced complexity models (RCM), to which, for example, the cellular automata (CA) approach belongs [9,10], represent an important alternative to computational fluid dynamics (CFD), suitable to be applied on a large area and over relevant time scales, both at reach and at catchment scale
For the study of the phenomena considered here, a suitable compromise can be found in approaches capable of simplifying the CFD technique, such as the widely used, simplified but effective ‘Shallow Water’ approach [11–15], as implemented in the RiverFlow2D calculation code [16] that was chosen to perform the simulations discussed

Summary

Introduction

The appropriate selection of an effective calculation tool constitutes the first action to be explored and pursued in order to obtain, as far as possible, a correct forecast of the evolution of possible impacting natural phenomena for the territory under observation. To avoid at least the further complexity of the geometric domain discretization, the meshless approach has been proposed and adopted In this context, the smoothed particle hydrodynamics (SPH) method appears to be quite well established [6–8].The mistaken was that Reduced complexity models (RCM), to which, for example, the cellular automata (CA) approach belongs [9,10], represent an important alternative to CFD, suitable to be applied on a large area and over relevant time scales (climate evolution as well), both at reach and at catchment scale. The options available in RiverFlow2D allow the inclusion of various topic models that are useful for civil protection, from debris flow simulations to urban floods and, through the option of parallel computing accessible on desktop and laptop (GPU), for a possible early-warning system [17–19]

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