published_or_final_version / Civil Engineering / Master / Master of Philosophy

Not available

published_or_final_version / abstract / toc / Chinese Historical Studies / Master / Master of Arts

This dissertation reports the results of a field based study examining sediment transport and bed mobility in a low-ordered, ephemeral watershed. Runoff and sediment transport concentrations were sampled at the watershed outlet to determine flow discharge and sediment flux during approximately 21 flow events, from 1998 - 2007. Sediment collected in flow was measured for grain-size distribution to determine if specific grain-size fractions behave differently while in transport. The coarse sediment yield was measured for mass and grain-size distribution at the watershed outlet for two years, 2005 - 2006. Further, the arrangement and composition of the channel bed material was comprehensively mapped using terrestrial-based photogrammetry for the years, 2005 - 2006. Results show that patterns of sediment transport are complex, controlled in part by flow hydraulics but also by other phenomena. Some of the variation in sediment transport is determined by grain-size. Grain-sizes with different sources within the watershed and that transported by different transport modes were observed to follow different patterns of transport. Also, the channel bed, which serves as the source for the coarse fraction of the sediment transport, was observed to change in grain composition during periods of flow. This tendency for the bed material to evolve in time likely affected the amount and composition of the sediment grains that were entrained from it.An additional objective of this dissertation was to determine how unique the observed patterns of sediment transport were to low-order ephemeral channels. Sediment transport and yield were modeled using bed load transport formulae designed to capture the physical mechanics of transport as observed in perennial streams. Results show that contemporary transport models predict transport within the field site with similar accuracy as that in many perennial systems but not well enough to rely on their predictions for many engineering applications.

This thesis examines the influence of lithology on debris torrent occurrence. The analysis covers a thirty-year period in 80 supply-limited basins distributed in the 400 km2 Tsitika River watershed, on northern Vancouver Island, British Columbia. Two bedrock types occur in the watershed, the Igneous Intrusive and the extrusive Karmutsen formations, covering forty-nine and fifty-one percent respectively. The debris torrent source basins are unlogged. The frequency data were obtained in the field using dendrochronological evidence of debris torrents. Field data were compared with data derived from air photographs, the latter were found to be unrepresentative of debris torrent occurrence and were not used. All study basins were digitised from 1 : 20 000 Terrain Resource Inventory Maps (TRIM), and were characterised by selected morphometric parameters. Results show that geology exerts significant control over the temporal and spatial occurrence of debris torrents in the Tsitika watershed; the Karmutsen formation is more prolific. Geology also was found to exert significant control over the runout area and volume of debris torrents. Climate, morphometry and surficial materials do not appear to be confounding parameters. Differences in weathering rates, infiltration patterns and detrital grain-size distribution associated with the two bedrock types are believed to account for the differences in debris torrent behaviour.

Large Central European flood events of the past have demonstrated that flooding can affect several river basins at the same time leading to catastrophic economic and humanitarian losses that can stretch emergency resources beyond planned levels of service. For Germany, the spatial coherence of flooding, the contributing processes and the role of trans-basin floods for a national risk assessment is largely unknown and analysis is limited by a lack of systematic data, information and knowledge on past events. This study investigates the frequency and intensity of trans-basin flood events in Germany. It evaluates the data and information basis on which knowledge about trans-basin floods can be generated in order to improve any future flood risk assessment. In particu-lar, the study assesses whether flood documentations and related reports can provide a valuable data source for understanding trans-basin floods. An adaptive algorithm was developed that systematically captures trans-basin floods using series of mean daily discharge at a large number of sites of even time series length (1952-2002). It identifies the simultaneous occurrence of flood peaks based on the exceedance of an initial threshold of a 10 year flood at one location and consecutively pools all causally related, spatially and temporally lagged peak recordings at the other locations. A weighted cumulative index was developed that accounts for the spatial extent and the individual flood magnitudes within an event and allows quantifying the overall event severity. The parameters of the method were tested in a sensitivity analysis. An intensive study on sources and ways of information dissemination of flood-relevant publications in Germany was conducted. Based on the method of systematic reviews a strategic search approach was developed to identify relevant documentations for each of the 40 strongest trans-basin flood events. A novel framework for assessing the quality of event specific flood reports from a user’s perspective was developed and validated by independent peers. The framework was designed to be generally applicable for any natural hazard type and assesses the quality of a document addressing accessibility as well as representational, contextual, and intrinsic dimensions of quality. The analysis of time-series of mean daily discharge resulted in the identification of 80 trans-basin flood events within the period 1952-2002 in Germany. The set is dominated by events that were recorded in the hydrological winter (64%); 36% occurred during the summer months. The occurrence of floods is characterised by a distinct clustering in time. Dividing the study period into two sub-periods, we find an increase in the percentage of winter events from 58% in the first to 70.5% in the second sub-period. Accordingly, we find a significant increase in the number of extreme trans-basin floods in the second sub-period. A large body of 186 flood relevant documentations was identified. For 87.5% of the 40 strongest trans-basin floods in Germany at least one report has been found and for the most severe floods a substantial amount of documentation could be obtained. 80% of the material can be considered grey literature (i.e. literature not controlled by commercial publishers). The results of the quality assessment show that the majority of flood event specific reports are of a good quality, i.e. they are well enough drafted, largely accurate and objective, and contain a substantial amount of information on the sources, pathways and receptors/consequences of the floods. The inclusion of this information in the process of knowledge building for flood risk assessment is recommended. Both the results as well as the data produced in this study are openly accessible and can be used for further research. The results of this study contribute to an improved spatial risk assessment in Germany. The identified set of trans-basin floods provides the basis for an assessment of the chance that flooding occurs simultaneously at a number of sites. The information obtained from flood event documentation can usefully supplement the analysis of the processes that govern flood risk. / Abschätzungen zum Hochwasserrisiko beschränken sich zumeist auf die Analyse innerhalb eines Einzugsgebietes bzw. eines bestimmten Ortes. Die Zusammenhänge in größeren Regionen und vor allem Korrelationen zwischen verschiedenen Einzugsgebieten werden nur selten betrachtet. Solche einzugsgebietsübergreifenden Analysen sind jedoch sowohl für die Versicherungswirtschaft, den Katastrophenschutz sowie für großräumige strategische Hochwasserplanungen notwendig. Allerdings stehen nur für eine geringe Auswahl historischer Ereignisse Daten zur Verfügung und systematische Ansätze zu ihrer Erfassung wurden für Deutschland bisher nicht entwickelt. Die vorliegende Studie untersucht zum ersten die Häufigkeit und Intensität von flussgebietsübergreifenden Hochwasserereignissen in Deutschland anhand von gemessenen Abflüssen an einer Vielzahl von Stationen. Es können insgesamt 80 Hochwasserereignisse in Deutschland im Zeitraum von 1952-2002 nachgewiesen werden. Davon treten die meisten Ereignissen im hydrologischen Winterhalbjahr auf (64%). Wir können nachweisen, dass die Häufigkeit des Auftretens in verschiedenen Perioden unterschiedlich ist, und dass im Untersuchungszeitraum eine signifikante Zunahme von Winterereignissen und damit vor allem von sehr schweren flussgebietsübergreifenden Hochwasserereignissen zu verzeichnen ist. Die Studie hatte des Weiteren zum Ziel, die verfügbare Daten- und Informationsgrundlage zur Hochwasseranalyse zu erkunden. Im speziellen wird untersucht, inwieweit Hochwasserereignisdokumentationen und verwandte Berichte als eine weitere Datenquelle für ein verbessertes Prozessverständnis genutzt werden können. Im Rahmen einer systematischen Suche konnten für die 40 größten Hochwasserereignisse in Deutschland 186 relevante Berichte identifiziert werden. 80% des Materials kann als Grauliteratur eingestuft werden, d.h. als Veröffentlichungen welche nicht durch kommerzielle Verleger publiziert wird. Die sich daraus ergebende Frage nach der Qualität der Dokumente und ihres Informationsgehaltes wurde durch die Entwicklung und Anwendung eines Qualitätsbewertungsschemas beantwortet. Die Ergebnisse der Qualitätsbewertung zeigen, dass die Mehrheit der ereignisspezifischen Hochwasserberichte von guter Qualität ist, d.h. die Berichte sind in ausreichender Qualität verfasst, größtenteils korrekt und objektiv und beinhalten eine substantielle Menge an Informationen zu den Ursachen, Verläufen, betroffenen Objekten und Schäden eines Ereignisses. Es wird empfohlen diese Informationen in die Wissenssynthese für die Hochwasserrisikobewertung einfließen zu lassen. Sowohl Ergebnisse als auch Daten dieser Studie sind so publiziert, dass sie öffentlich zugänglich sind und für weitere Forschungsfragen genutzt werden können.

Flooding is the most devastating natural hazard in Pakistan and the recent flooding has demonstrated its severeness. Floods are common all over the country, though the province of Sindh experience the most damages. River Indus flows on a ridge here and once the surplus water during flood events leave the main channel does not return back. Therefore it is very important to adapt to this disaster. This study aims at identifying ways to address the problem of floods in upper Sindh for which Sukkur district was chosen. Questionnaire survey and interviews were conducted in three talukas of the district in the aftermath of recent floods (2010, 2011 and 2012) to provide a baseline study for Sustainable Flood Disaster Management Plan for the upper Sindh region. Recommendations were put to reduce the flood losses for the future floods.

There is growing concern in the United States and abroad that changes in climate may have serious adverse impacts on communities and their civil infrastructure systems. In response, governments and agencies have begun to investigate adaptation: actions taken to reduce the vulnerability or increase the resiliency of natural and human systems in light of expected climate change. In the transportation sector, adaptation planning has predominantly pursued risk-based strategies that seek to identify climate impacts, and assess infrastructure vulnerabilities across multiple asset types, in network-level planning. However, given the complexity of the myriad asset types of which engineered civil infrastructure systems are composed, these frameworks may not adequately address the unique concerns of these various individual asset types. This research develops a risk-based framework to assess and prioritize at a network-level the risks of highway culvert assets to the projected impacts of climate change, specifically focusing on increases in extreme precipitation, and the associated potential for flooding. The framework is applied in a series of case studies using culvert management data provided by four state DOTs, and national climate change projection and infrastructure datasets. The framework developed proposes a new characterization of infrastructure climate change risk, based upon the catastrophe model, to address the need for qualitative approaches to risk given the uncertain nature of climate change, and the sometimes sparse inventory and attribute data for various assets. This characterization proposes three “dimensions” of infrastructure climate risk (climate change impact exposure, asset climate impact vulnerability, and asset criticality) to assign culvert asset priorities. The research develops a method to project the geospatial extent and changes in magnitude of extreme precipitation events; it also develops two measures of culvert vulnerability to increased flow conditions based upon data collected in general culvert management activities. This research demonstrates that existing data sources can be reasonably combined in an analytical assessment framework to identify climate change impact risks to highway culvert assets, providing an additional resource to the existing climate change adaptation planning and risk management toolkit in the transportation infrastructure sector, and also laying a foundation for further refinement of these methods. The results of this research demonstrate that existing climate change projection data, when used alongside culvert inventory and attribute data, provides a reasonable means by which to analyze the projected exposure of culvert assets to climate change impacts. This research also demonstrates that existing culvert management data provides a reasonable foundation upon which to assess the relative vulnerability of culverts to increased flow conditions, although additional research is necessary to develop these methods. The structure of the proposed framework provides a viable means by which quantitative climate change projections, asset vulnerability, and asset criticality data can be combined in a mixed-methods approach to qualitatively characterize climate change impact risks to highway culvert assets despite uncertainty in climate change projections and other inputs.

The aim of this research project was to estimate parameters for the distribution of annual maximum flood levels for the Zambezi River at Katima Mulilo. The estimation of parameters was done by using the maximum likelihood method. The study aimed to explore data of the Zambezi's annual maximum flood heights at Katima Mulilo by means of fitting the Gumbel, Weibull and the generalized extreme value distributions and evaluated their goodness of fit.

No description available.