Dam-Break Wave Propagation in Alpine Valley with HEC-RAS 2D: Experimental Cancano Test Case

TLDR

Flood modeling with 2D shallow‑water equations is routine, and although HEC‑RAS 2D has performed well in many test cases, few validations exist for dam‑break floods on steep, irregular bathymetries. The study evaluates HEC‑RAS 2D by comparing its simulated discharge hydrographs with measurements from a Froude‑simulated physical model of the Cancano I dam collapse and its 15‑km downstream wave propagation. The authors generate discharge hydrographs from a historical physical model built in Froude similitude and compare them with HEC‑RAS 2D simulations of the dam‑break wave along the alpine valley. The simulations reproduce the experimental hydrographs and flooded areas, agree closely with TELEMAC 2D results, confirming HEC‑RAS 2D’s suitability for steep alpine valley dam‑break studies, and the test data are released for community validation.

Abstract

Flood modeling by numerical solution of the two-dimensional (2D) shallow-water equations is ordinary practice. HEC-RAS 2D was recently released along with a suite of test cases showing the very good performance of the code in many practical situations. However, validation test cases aimed at demonstrating the capability of the software to deal with dam-break floods on very steep and irregular bathymetries are very limited. This paper tests HEC-RAS 2D against the discharge hydrographs measured in a historical physical model built in Froude similitude to analyze the consequences of the hypothetical collapse of the Cancano I dam (northern Italy) and the propagation of the resulting dam-break wave along the 15-km reach of the downstream alpine valley. The experimental hydrographs and the measured extent of the flooded areas are well reproduced by the numerical simulations. Moreover, the results obtained with HEC-RAS 2D are in very good agreement with those obtained using TELEMAC 2D, which confirms the suitability of the HEC-RAS 2D software for dam-break flood studies in steep alpine valleys. The data of the test case are made available to the scientific community for validation purposes.