<p> Studies to date involving the network properties of drainage systems have been theoretical in nature; and the environmental implications of these network characteristics have not been exploited to the extent that would appear warranted. This situation exists due to the lack of an accurate data source. Many studies have recognized this. inadequacy of the conventional data sources to meet the necessary requirements of efficiency (in data production and handling), accuracy, consistency and uniformity. </p> <p> The present study demonstrates that high altitude, small scale colour infrared photography is capable of providing drainage network data that fulfill all these basic requirements. Data derived from the three drainage basins, mapped from a variety of data sources, demonstrate three important points. The level of detail obtained from the small scale colour infrared photography far exceeds that available from more traditional data sources. Secondly, these network data are statistica+ly consistent with the traditional data sources. Thirdly, the basin characteristics derived from the high altitude data source show a marked association with the known surficial environments and an expected variation from one surficial environment to another. </p> / Thesis / Master of Arts (MA)

Critical infrastructure networks (CIN) are essential systems that provide key socio-eco-nomical services. They can be classified into different sectors such as energy supply, in-formation and communication, water, food, health, transport, among others. Their pro-tection from hazards and constant improvements are crucial for ensuring the appropriate operation of a society and economy. In this context, the current study focused on analyzing the factors affecting the function-ing of one particular CIN in the water sector: the urban drainage networks (UDNs). More specifically, the present research focused on evaluating how does the structure of UDNs influence their function. Concepts and methods from complex network theory were used to evaluate structural properties of sewers systems and function was evaluated in terms wastewater flow quantitates and occurrence of node flooding and combined sewer over-flow (CSOs) events, considered as indicators if network performance. Initial results suggested that network metrics can be used as surrogate variables of UDNs main functions, i.e. transport and collection of wastewater. However, efficiency of this de-pended on the type of layout, i.e. physical arrangement of the network. Following studies focused then on developing a graph-theory based method to quantify the structure of an UDN and use it to evaluate the influence of layout on its function. Results suggested that sewer networks with a more meshed layout had a better performance, i.e. adverse events such as urban pluvial flooding and CSO discharges were less likely to occur, than UDNs with a branched layout. Furthermore, transitioning from a tree-like structure to a more meshed system was identified to be a cost-efficient measure for urban flooding manage-ment. It is concluded that the structure of an UDN, in terms of its layout, has a strong influence on its performance and therefore on its resilience. It is expected that the obtained results could serve as support for better management and operational actions of UDNs and could also serve as basis for the development of a new structural resiliency analysis based mainly on the UDN configuration.:1. General Introduction 2. Centrality and Shortest Path Length measures for the functional analysis of Urban Drainage Networks 3. Meshness of sewer networks and its implications for flooding occurrence 4. The Role of Sewer Network Structure on the Occurrence and Magnitude of Combined Sewer Overflows (CSOs) 5. Determination of Optimal Meshness of Sewer Network Based On a Cost-Benefit Analysis 6. Influence of Meshness on Urban Drainage Networks Resilience and its Implications 7. Conclusions and Outlook 8. Supplementary Information