Modelling wind-driven rain on buildings in urbanized area using 3-D GIS and LiDAR datasets

This study investigated the distribution of the fraction of rainfall intercepted by the facades of buildings located in an urbanized area. We used the frequently used semi-empirical standard ISO-15927-3 to simulate Wind-Driven Rain on facades. The implementation of the Norm on a neighbourhood scale required a list of parameters, including building geometry and terrain characteristics. For the first time, we proposed the use of combined 3-D GIS and LiDAR data to retrieve all the information necessary to apply the Norm on a large set of buildings. The proposed methodology was tested on a dense urban area of 242 buildings with a wide range of original features. The distributions of simulated catch ratios per facade were exponentially distributed between 0 and 9%. Results obtained were smaller than those usually identified in the literature. This was in large part explained by two points: (i) the buildings considered are located in a dense urban area where surrounding buildings create an obstruction factor that limits WDR on facades and, (ii) not only are windward facades considered, but also facades located in the dominant wind direction which received almost no rain. Facade orientation is a clear factor that influenced the amount of rainfall in contact with it. Modern GIS techniques are sufficiently advanced to provide the necessary information to assess WDR. However, the accuracy of our conclusion was limited by the inherent simplicity of the Norm, which has potential for improvement in terms of the definition of the obstruction factor and the range of building geometry which it takes into consideration. 2012 Elsevier Ltd. All rights reserved.