A disposition of interpolation techniques

A large collection of interpolation techniques is available for application in environmental research. To help environmental scientists in choosing an appropriate technique a disposition is made, based on 1) applicability in space, time and space-time, 2) quantification of accuracy of interpolated values, 3) incorporation of ancillary information, and 4) incorporation of process knowledge. The described methods include inverse distance weighting, nearest neighbour methods, geostatistical interpolation methods, Kalman filter methods, Bayesian Maximum Entropy methods, etc. The applicability of methods in aggregation (upscaling) and disaggregation (downscaling) is discussed. Software for interpolation is described. The application of interpolation techniques is illustrated in two case studies: temporal interpolation of indicators for ecological water quality, and spatio-temporal interpolation and aggregation of pesticide concentrations in Dutch surface waters. A valuable next step will be to construct a decision tree or decision support system, that guides the environmental scientist to easy-to-use software implementations that are appropriate to solve their interpolation problem. Validation studies are needed to assess the quality of interpolated values, and the quality of information on uncertainty provided by the interpolation method

Rainfall threshold definition using an entropy decision approach and radar data

Flash flood events are floods characterised by a very rapid response of basins to storms, often resulting in loss of life and property damage. Due to the specific space-time scale of this type of flood, the lead time available for triggering civil protection measures is typically short. Rainfall threshold values specify the amount of precipitation for a given duration that generates a critical discharge in a given river cross section. If the threshold values are exceeded, it can produce a critical situation in river sites exposed to alluvial risk. It is therefore possible to directly compare the observed or forecasted precipitation with critical reference values, without running online real-time forecasting systems. The focus of this study is the Mignone River basin, located in Central Italy. The critical rainfall threshold values are evaluated by minimising a utility function based on the informative entropy concept and by using a simulation approach based on radar data. The study concludes with a system performance analysis, in terms of correctly issued warnings, false alarms and missed alarms

FRAMEWORK FOR THE FULLY PROBABILISTIC ANALYSIS OF EXCAVATION-INDUCED SERVICEABILITY DAMAGE TO BUILDINGS IN SOFT CLAYS

In this dissertation, a framework for a fully-probabilistic analysis of the potential for building serviceability damage induced by an excavation in soft clays is established. This analysis framework is established based on the concept of a serviceability limit state where the resistance is represented by the capacity of a building to resist serviceability damage, and the loading is represented by the demand on a building due to excavation-induced ground movements. In this study, both the resistance and the loading are treated as a random variable; the resistance is characterized empirically based on a database of the observed building performance while the loading is estimated for a specific case using semi-empirical models that were created with the results of finite element analysis and field observations. A simplified procedure is developed for estimating the loading on a building induced by an excavation. In this simplified procedure, the loading is expressed in terms of damage potential index (DPI) that is based on the concept of principal strain. On the other hand, the resistance as a random variable is characterized based on observed building performance, also in terms of the DPI. The uncertainties of both the resistance and the loading are fully characterized in this dissertation study to enable a fully probabilistic analysis. The developed framework for the fully-probabilistic assessment of the potential for excavation-induced building damage is demonstrated with the well-known TNEC case history. Finally, since the observational method is commonly applied to the design and construction of excavation systems, a simplified scheme for updating the soil parameters (and consequently DPI) based on the observations of the maximum wall deflection and ground settlement is developed. This updating scheme is demonstrated with an excavation case history and shown to be an effective technique for monitoring the damage potential of buildings adjacent to an excavation. The developed framework allows for fully-probabilistic assessment of the potential of building damage induced by an excavation, and thusly, provides engineers with a more transparent assessment of the risk associated with a particular excavation design and construction. Furthermore, with the observational method, the potential for excavation-induced serviceability damage can be reassessed as the excavation proceeds. With this approach, the excavation system can be monitored as the excavation proceeds and necessary measures can be taken to prevent damage to buildings adjacent to the excavation