The impact of uncertainty in satellite data on the assessment of flood inundation models

The performance of flood inundation models is often assessed using satellite observed data; however these data have inherent uncertainty. In this study we assess the impact of this uncertainty when calibrating a flood inundation model (LISFLOOD-FP) for a flood event in December 2006 on the River Dee, North Wales, UK. The flood extent is delineated from an ERS-2 SAR image of the event using an active contour model (snake), and water levels at the flood margin calculated through intersection of the shoreline vector with LiDAR topographic data. Gauged water levels are used to create a reference water surface slope for comparison with the satellite-derived water levels. Residuals between the satellite observed data points and those from the reference line are spatially clustered into groups of similar values. We show that model calibration achieved using pattern matching of observed and predicted flood extent is negatively influenced by this spatial dependency in the data. By contrast, model calibration using water elevations produces realistic calibrated optimum friction parameters even when spatial dependency is present. To test the impact of removing spatial dependency a new method of evaluating flood inundation model performance is developed by using multiple random subsamples of the water surface elevation data points. By testing for spatial dependency using Moran’s I, multiple subsamples of water elevations that have no significant spatial dependency are selected. The model is then calibrated against these data and the results averaged. This gives a near identical result to calibration using spatially dependent data, but has the advantage of being a statistically robust assessment of model performance in which we can have more confidence. Moreover, by using the variations found in the subsamples of the observed data it is possible to assess the effects of observational uncertainty on the assessment of flooding risk

Toward a Principled Statutory Approach to Supplemental Jurisdiction in Diversity of Citizenship Cases

Symposium: A Reappraisal of the Supplemental-Jurisdiction Statute: Title 28 U.S.C. § 1367

Toward a Principled Statutory Approach to Supplemental Jurisdiction in Diversity of Citizenship Cases

Symposium: A Reappraisal of the Supplemental-Jurisdiction Statute: Title 28 U.S.C. § 1367

Front-Loading, Avoidance, and Other Features of the Recent Supreme Court Class Action Jurisprudence

This Article discusses each of the thirteen Supreme Court decisions with the goal of drawing at least tentative conclusions for their impact on federal class practice. The thirteen decisions may be placed into five groups. Only three of the cases directly involve the general interpretation and application of Rule 23, while the other ten fall into four particular substantive areas. Reflecting these divisions, this Article proceeds in five parts. Part I discusses the three cases directly interpreting Rule 23. Part II addresses the three decisions involving securities classes brought under Rule 10b-5. Part III discusses the three decisions involving the Federal Arbitration Act. Part IV engages the two decisions addressing the non-party status of class members. And Part V concerns those decisions interpreting specialized grants of federal jurisdiction