The use of remote sensing imagery for monitoring recovery in the aftermath of a natural disaster: the Hurricane Katrina Case

Although Recovery is often defined as the less studied and documented phase of the Emergency Management Cycle, a wide literature is available for describing characteristics and sub-phases of this process. Previous works do not allow to gain an overall perspective because of a lack of systematic consistent monitoring of recovery utilizing advanced technologies such as remote sensing and GIS technologies. Taking into consideration the key role of Remote Sensing in Response and Damage Assessment, this thesis is aimed to verify the appropriateness of such advanced monitoring techniques to detect recovery advancements over time, with close attention to the main characteristics of the study event: Hurricane Katrina storm surge. Based on multi-source, multi-sensor and multi-temporal data, the post-Katrina recovery was analysed using both a qualitative and a quantitative approach. The first phase was dedicated to the investigation of the relation between urban types, damage and recovery state, referring to geographical and technological parameters. Damage and recovery scales were proposed to review critical observations on remarkable surge- induced effects on various typologies of structures, analyzed at a per-building level. This wide-ranging investigation allowed a new understanding of the distinctive features of the recovery process. A quantitative analysis was employed to develop methodological procedures suited to recognize and monitor distribution, timing and characteristics of recovery activities in the study area. Promising results, gained by applying supervised classification algorithms to detect localization and distribution of blue tarp, have proved that this methodology may help the analyst in the detection and monitoring of recovery activities in areas that have been affected by medium damage. The study found that Mahalanobis Distance was the classifier which provided the most accurate results, in localising blue roofs with 93.7% of blue roof classified correctly and a producer accuracy of 70%. It was seen to be the classifier least sensitive to spectral signature alteration. The application of the dissimilarity textural classification to satellite imagery has demonstrated the suitability of this technique for the detection of debris distribution and for the monitoring of demolition and reconstruction activities in the study area. Linking these geographically extensive techniques with expert per-building interpretation of advanced-technology ground surveys provides a multi-faceted view of the physical recovery process. Remote sensing and GIS technologies combined to advanced ground survey approach provides extremely valuable capability in Recovery activities monitoring and may constitute a technical basis to lead aid organization and local government in the Recovery management.

A first survey on the status of the Posidonia oceanica meadow in Calpe Bay (Alicante, Spain).

Posidonia oceanica, endemic seagrass of the Mediterranean Sea, forms extensive meadows. It is included among the Mediterranean protected habitats by the Habitat Directive (92/43/EEC). P. oceanica meadows are exposed to anthropogenic impacts that are more evident in areas close to cities, ports or areas with a large coastal tourism development. Mean exponential decline rate of 5 % yr-1 is estimated for the Spanish meadows. If this trend is maintained, most of the meadows are predicted to halve in shoot density over the next 20 years. The meadows regression can give way to a new regime, which supposes the loss of the multiple services that the meadows provided. It is necessary to recognize situations of stress in time, before irreversible damages and changes towards alternative regimes are evident. This study has been carried out in Calpe Bay, Alicante (Spain), during May and June 2017, with the aim of assessing, for the first time, the status of the P. oceanica meadows providing a baseline data for the future monitoring scheme. The features and status of the seagrass beds have been assessed by physical, physiographical, structural and functional descriptors. The results showed that the health status classification of P. oceanica meadows in Calpe Bay vary between “equilibrium” and “disturbed”. The “disturbed” conditions were observed in a shaded area where it is probably due to the low solar radiance. In a lower limit in a shallow meadow, where it could be due to the combined effect of substrate structure and hydrodynamic regime. Finally in a touristic area where patchy impacts could be attributed to direct human disturbance (e.g. anchoring). Overall the status of P. oceanica meadows in Calpe bay is not worrying. However, it is important to develop monitoring plans to assess the dynamics of the seagrass detecting any early decline symptom in order to act, as soon as possible because, when a regression of a meadow is produced, it could not be recovered at human scales.

Real-time PMU monitoring of an IEEE 5-Bus Network implemented on OPAL system

This thesis studies the state-of-the-art of phasor measurement units (PMUs) as well as their metrological requirements stated in the IEEE C37.118.1 and C37.118.2 Standards for guaranteeing correct measurement performances. Communication systems among PMUs and their possible applicability in the field of power quality (PQ) assessment are also investigated. This preliminary study is followed by an analysis of the working principle of real-time (RT) simulators and the importance of hardware-in-the-loop (HIL) implementation, examining the possible case studies specific for PMUs, including compliance tests which are one of the most important parts. The core of the thesis is focused on the implementation of a PMU model in the IEEE 5-bus network in Simulink and in the validation of the results using OPAL RT-4510 as a real-time simulator. An initial check allows one to get an idea about the goodness of the results in Simulink, comparing the PMU data with respect to the load-flow steady-state information. In this part, accuracy indices are also calculated for both voltage and current synchrophasors. The following part consists in the implementation of the same code in OPAL-RT 4510 simulator, after which an initial analysis is carried out in a qualitative way in order to get a sense of the goodness of the outcomes. Finally, the confirmation of the results is based on an examination of the attained voltage and current synchrophasors and accuracy indices coming from Simulink models and from OPAL system, using a Matlab script. This work also proposes suggestions for an upcoming operation of PMUs in a more complex system as the Digital Twin (DT) in order to improve the performances of the already-existing protection devices of the distribution system operator (DSO) for a future enhancement of power systems reliability.