Dissertations / Theses on the topic 'Flooding in river urban systems'

- Description of the problems

Throughout history floods have been one of the most severe natural catastrophes, which brought about loss of lives and huge economic losses in addition to the influence on community activities and adverse effects on the environment. We have witnessed enormous flood events almost all over the world, even in the early years of 21st century. The cruel lesson learnt is that we have not coped well with floods.

Studying the risk of flooding is the goal of this thesis. The focus is given to flooding of urban drainage systems. Urban climate, human activities and land use vary quickly and greatly with time. These variations modify the features of both urban hydrology and hydraulics, and change the distribution of water. It may lead to dual adverse effects in one region: the severe water shortage in one period and the increasing risk of flooding in another period. Therefore, finding appropriate solutions for these problems has been being a great challenge for the whole world.

- Aims of this study

This study aims to contribute ideal approaches and models to understand deeply urban flooding problems, i.e. to find the causes of flooding, to analyze their propagations and on this basis to evaluate the risk of flooding, and finally to search for solutions for flood mitigation.

- Study contents and methodologies

Distinguishing the potential hazards of urban flooding, delineating the changes of urban lands, developing models to simulate flooding and examining different measures to mitigate the risk of flooding constitute the main contents of this study. It is carried out by both qualitative analysis and quantitative simulations in a stepwise manner. Regarding the stochastic characteristics of flooding, a risk analysis initiates the study, which aims to formulate flooding scenarios in general urban environment through procedures of system definition, hazard identification, causal analysis, frequency analysis, consequence estimation and mitigation. A Norwegian case study illustrates the whole process.

Following the risk analysis, GIS technology is introduced to delineate the variation of topography. GIS hydrological modeling is applied to delineate the basic hydrological elements from a Digital Elevation Model (DEM). The accuracy of grid DEM and the influence of buildings are studied.

Two urban flooding models, the "basin" model and the dual drainage model, are developed on the basis of the MOUSE program (DHI, 2000). The three models, i.e. the MOUSE model, the “basin” model and the dual drainage model, are examined through two case studies, and the flow capacities of the existing sewers in these two case studies are then checked. Following the flooding simulation, the effectiveness of four flooding mitigation measures is tested.

- Main results

Sixty-eight (68) potential flooding hazards are identified by risk analysis in Chapter three. In combination with Trondheim case study, the frequencies of several flooding scenarios are studied, and it is indicated that the flooding of urban drainage systems happens more frequently than river flooding. When it happens, urban flooding disturbs very much the activities in flooding areas. Therefore management attentions should be paid to urban flooding in addition to large river flooding.

GIS is used as a bridge between digital data and numerical flooding simulation. Two important hydrological elements, watersheds and surface stream networks, are derived from grid DEM in Chapter four. The preliminary flood risk zones are delineated in combination with two case studies. They provide useful information for flood management.

The three flooding models are calibrated through two case studies: Trondheim- Fredlybekken catchment in Norway and Beijing-Baiwanzhuang (BWZ) catchment in China. Flooding checking of the existing sewer systems in these two case studies indicates that the current flow capacities of sewers are less than the designed capacities. Consequently, flood mitigation measures are examined in the following Chapter six. The study indicates that the combination of structural and non-structural flood mitigation measures are regarded as the comprehensive solution for flood control.

- Restrictions of the developed models

The developed flood models are restricted to summer and autumn flooding situations. In other words, the snowmelt routine is not included in the hydrological model applied. However, if a hydrological model that is able to simulate snowmelt could be connected to the developed models, then the hydraulic analysis would be carried out similarly.

The research presented in this thesis addressed the performance of Sustainable Urban Drainage Systems (SUDS) at three sites in Scotland - a porous paved car park and two swales. It is the first research to provide results for such systems in the UK and also the first direct comparison between SUDS and traditional systems in situ. The aim of developing guidance on effectiveness and synthesising design recommendations has been achieved with the integration of hydrological and water quality studies together with modeling. Monitoring data and information were analysed on both a site-by-site basis and as a comparison between sites. Hydrological and water quality data were collected at each site. Key hydraulic parameters examined include percentage runoff, initial runoff loss, peak flow reduction and lag time. The term Benefit Factor has been introduced as a volumetric measure used to summarise the hydraulic benefit gained by installing SUDS, as no comparable terminology has yet been used elsewhere. The water quality parameters include physical/ chemical, hydrocarbons and metals. All three sites had low levels of pollution with little scope for water quality improvement, however the changes in water quality did indicate the different processes occurring within the systems. Computer models were built for the porous paving installation and one of the swales, further to understand the processes of source control and to analyse the systems. Hydraulic capacity exceedence criteria were investigated using design storms, and finally the models were used to evaluate improvements to design detailing. The results of this research have shown that, despite being under-designed according to current guidance, all three sites performed very favourably. The performance of porous paving and swales can be similar depending on design and detailing. A number of design recommendations are made as a result of observations and sensitivity analysis, and these should be considered in conjunction with current guidance.

Many urban rivers receive significant inputs of metal-contaminated sediments from their catchments. Their restoration has the potential to increase the deposition and accumulation of these sediments from greater sediment supply and increased channel hydraulic complexity, creating a store of metals which could have negative impacts upon ecosystems and human health. Macrophytes often establish in restored channels and have the potential to stabilise these sediments and uptake metals through processes of phytoremediation, thus reducing the risk of the accumulated sediments becoming a source of metals. This thesis investigates the effects of river restoration upon sedimentation patterns and the interactions between macrophytes and sediments in terms of sediment trapping, stabilisation and metal uptake within urban river systems. At a reach scale, greater finer sediment deposition and the accumulation of sediment around in-channel vegetation was found within restored stretches of tributaries of the River Thames London, reflecting sediment availability and hydraulic conditions. These sediments were important in terms of greater metal storage within stretches, and along with gravels showed particularly high metal concentrations. Interactions between macrophytes, sediment and flow were investigated within the urban-influenced River Blackwater, Surrey. At the stand scale, the common emergent Sparganium erectum was found to significantly reduce flow velocities, accumulate fine sediments and retain them over winter. Research on individual plants revealed that, although three common emergent macrophytes (Sparganium erectum, Typha latifolia and Phalaris arundinacea) did not significantly phytoremediate metal contaminated sediments through metal uptake or bioconcentration, the reinforcement and stabilisation of these accumulated sediments (particularly by Sparganium erectum and Typha latifolia) and the creation of anoxic sediment conditions which strongly bind metals, were important in reducing the risk of metal mobilisation from the sediments. These macrophyte sediment interactions illustrate the great potential of using emergent macrophytes in the restoration and management of urban rivers with metal contaminated sediments.

Flood hazard assessment and mapping is a necessary step to define flood risk reduction strategies and to develop risk management plans. Anyway, in Italy, and in particular in Lombardy Region, legislation provides only vague indications on how to assess flood hazard, therefore the definition of risk is lacking in a scientific basis, and wide space is left to subjectivity and to approximate analyses. This PhD research aims to improve the topic presenting an approach for flood hazard analysis and mapping that fits the Lombardy Region legislative framework, but introduces a level of experimental modelling. The approach has been applied on an area located in the medium Valtellina (Alps, northern Italy) – 26 km2 wide – and makes use of advanced flood modelling tools, in order to support the development of Emergency Plans and to provide suggestions to deepen the analyses required for Urban Planning. Hydrologic and hydraulic conditions of the site are quite complex, and data availability is not optimal. Therefore, several modelling strategies (1D, 2D and combined 1D2D approaches) and three software packages (SOBEK, FLO-2D and FloodArea) were tested and results were compared and discussed. Lots of efforts have been spent in trying to define an accurate topographical description: a TIN was constructed from available 3D cartography and cross sections profiles, then converted into a DEM. Institutional values of peak discharges for the return times of 20, 100 and 200 years were used to construct input hydrographs. Roughness coefficients were set according to literature tables and available local studies, and their influence on models behaviour was tested through sensitivity analyses. Difficulties related to some of the models and/ or verification of inappropriate results led to exclude two software packages and to select SOBEK 1D2D as the most suitable tool for flood modelling in the study area. Results were converted into hazard maps useful for both the purposes of Civil Protection and Urban Planning, basing on an innovative method, including an expression of uncertainty. Most of the complexities of the issue are analysed and discussed, referring to a wide literature background, which the research will contribute to enrich.

Mestrado em Arquitectura Paisagista - Instituto Superior de Agronomia
The present climate changes constitute one of the main threats to delta and estuary cities. The rise of the mean sea level and the increase of the intensity and frequency of the precipitation extremes are presently raising the flood risk of these territories, jeopardizing their maintenance and future development. The present work focuses on how these climate change processes can raise the risk of the urban drainage flooding events at the cities waterfronts. The relevance of the problem is reinforced by the present incapacity of the urban drainage systems to follow the needed adaptation, forcing the delta and estuary cities to rethink the management of their storm water outflow. Under this view, the main drainage adaptation strategies and measures are analysed, namely in urban planning and design, and on the benefits of the integration of natural processes. To contextualize the addressed problem, the possible drainage flood impacts over the Lisbon riverfront are analysed. The influence of the climate change processes over the current drainage system and the flood risk of this area are shown, demonstrating the need for integration of the drainage problem in the future urban planning.

In future cities, urban drainage and flood management systems should be designed not only to reliable during normal operating conditions but also to be resilient to exceptional threats that lead to catastrophic failure impacts and consequences. Resilience can potentially be built into urban drainage systems by implementing a range of strategies, for example by embedding redundancy and flexibility in system design or rehabilitation to increase their ability to efficiently maintain acceptable customer flood protection service levels during and after occurrence of failure or through installation of equipment that enhances customer preparedness for extreme events or service disruptions. However, operationalisation of resilience in urban flood management is still constrained by lack of suitable quantitative evaluation methods. Existing hydraulic reliability-based approaches tend to focus on quantifying functional failure caused by extreme rainfall or increases in dry weather flows that lead to hydraulic overloading of the system. Such approaches take a narrow view of functional resilience and fail to explore the full system failure scenario space due to exclusion of internal system failures such as equipment malfunction, sewer (link) collapse and blockage that also contribute significantly to urban flooding. In this research, a new analytical approach based on Global Resilience Analysis (GRA) is investigated and applied to systematically evaluate the performance of an urban drainage system (UDS) when subjected to a wide range of both functional and structural failure scenarios resulting from extreme rainfall and pseudo random cumulative link failure respectively. Failure envelopes, which represent the resulting loss of system functionality (impacts) are determined by computing the upper and lower limits of the simulation results for total flood volume (failure magnitude) and average flood duration (failure duration) at each considered failure level. A new resilience index is developed and applied to link resulting loss of functionality magnitude and duration to system residual functionality (head room) at each considered failure level. With this approach, resilience has been tested and characterized for a synthetic UDS and for an existing UDS in Kampala city, Uganda. In addition, the approach has been applied to quantify the impact of interventions (adaptation strategies) on enhancement of global UDS resilience to flooding. The developed GRA method provides a systematic and computationally efficient approach that enables evaluation of whole system resilience, where resilience concerns ‘beyond failure’ magnitude and duration, without prior knowledge of threat occurrence probabilities. The study results obtained by applying the developed method to the case studies suggest that by embedding the cost of failure in resilience-based evaluation, adaptation strategies which enhance system flexibility properties such as distributed storage and improved asset management are more cost-effective over the service life of UDSs.

The research programme was relevant to urban planning and in particular to the design of stormwater management schemes that are more environmentally and socially acceptable. It examined social and perception issues relating to stormwater management techniques within residential areas, and in particular to the application of SUDS, mainly ponds, and river management schemes. The thesis arose from a project funded by the Environment Agency of England and Wales through SNIFFER under a programme titled “Social impacts o f stormwater management techniques including river management and SUDS”, SNIFFER Code: SUDS01. The public perception of construction is becoming a matter of increasing importance both in the UK and internationally since socio-economic parameters and public consultation both have to be taken into consideration in the planning and implementation of relevant projects. This research programme endeavoured to match the relevant legislative goals with society’s actual needs. The main aims of the research programme were to obtain an in-depth understanding and knowledge of the perceptions of popular stormwater management practices (SUDS and river management), and to evaluate these techniques from a social perspective. To satisfy these aims the following objectives were set: • To assess public awareness and perceptions of SUDS (particularly retention ponds) in the UK; • To assess professional perceptions of SUDS in the UK; • To assess perceptions of different stormwater management techniques, in three European cities; • To compare perceptions of different stormwater management techniques, SUDS and river management practices; • To link the research findings with trends in perceptions of nature and water. To meet the programme’s aims and to satisfy the objectives, the perceptions of SUDS in the UK (principally ponds) were investigated over a wide range of locations. In addition, the different river management approaches used in three heavily urbanised European cities, Glasgow, London, and Athens were investigated. The results of this research programme provide a means to understand perceptions of stormwater management and to appreciate what types of schemes will be more readily accepted by the public. The research has shown that members of the public hold strong views as to what they like or dislike about SUDS and water management installations in their local area, in spite of the fact that there were demonstrably low levels of public awareness of SUDS. The amenity, recreational value and aesthetics of new schemes seem to be of major importance for public acceptability, while function, efficiency, and maintenance are primarily important in areas facing flooding problems. Other key findings include the fact that there is a general preference for sustainable urban water management and for river restoration schemes compared with more conventional, ‘hard engineering’ approaches, such as culverting of rivers. This preference was expressed both by members of the public and by professionals involved in their planning and implementation. Another important result was that although unfamiliarity can produce negativity, education can influence attitudes positively even in sensitive issues such as safety, and can be used by authorities and planners as a means of enhancing the acceptability of new schemes. Consequently, the results of the surveys can be used as arguments towards the application of informative campaigns which should be taken into account prior to scheme implementation. This information can be utilised not only for stormwater management design, but also for other environmentally friendly constructions which the public may have a low level of awareness. Recommendations are made with respect to public and professional attitudes for improving the public acceptability of new and modified stormwater management systems. Recommendations and barriers to the uptake outlined in this thesis mainly refer to the appearance of schemes rather than technical issues. They are therefore of most use as guidance for improving aesthetics and increasing public acceptability. The outcomes of this research will be of use to policy makers, water companies, local authorities, environment agencies, planners, developers, consultants active in urban development, and researchers in applying wider-accepted practices for the assessment of public perception. Some findings from this research have been presented at several stakeholders’ meetings, at 4 conferences, and are published in the form of papers and reports, including the DTI SR 622 report titled “An Assessment of the Social Impacts of Sustainable Drainage Systems in the UK”, and the Environment Agency & SNIFFER report, SUDS01, 2005, titled “Social Impacts of stormwater management techniques including river management and SUDS”. This publication also constitutes Environment Agency R&D Technical report P2-258.

Urban pluvial flooding is stressing urban areas with increasing frequency, becoming a factor of great concern. Soil sealing resulting from urban development is one of the main reasons for changes in natural hydrological processes and related recurring failures of urban drainage systems, especially during heavy rainfall events. Today, several studies are looking at the concept of urban resilience as a new paradigm, for a better integration of issues of water and flood risk with urban planning. Resilience is viewed as a way to tackle risk, showing bonds with its different sections, among which the flood hazard. It is broadly agreed that spatial planning, by incorporating Sustainable urban Drainage Systems (SuDS) within tools and polices, helps to build urban flood resilience. In particular, SuDS, as alternative strategy for surface water management, could potentially address anthropogenically generated hazard, thanks to the water-flow regulating service and benefits they provide. This research explores the relationship between the risk of urban pluvial flooding, resilience and urban planning. Particularly, the concept of resilience is clarified in order to highlight how it contributes to both analyse urban systems by adding levels of knowledge, and steer planning and policy approaches towards the mitigation of pluvial flood risk. By applying a research methodology based on the use of EPA-Storm Water Management Model (SWMM), the main aim of the thesis was to define a proper methodology and to build-up an analytical tool in order to analyse and assess the urban system s response to rainfall events, and to be used during and for purposes of the planning process. The proposed methodology is open to be flexibly applied to aptly handle the previous issues. Accordingly, the purpose was twofold: to assess the impact of masterplan in terms of increase of flow peak releases from urban catchments concerned by planned urban developments; to examine the urban system s reaction to rainfall and to evaluate how the response is affected by SuDS implementation at the catchment level. Case study areas were selected in the cities of Catania and Avola, in Sicily, for which masterplans design has been recently proposed by local planning authorities. Simulation of scenarios were carried out for a number of design storm events of selected return periods. Input parameters for the modelling were derived from urban analyses and hydrologic analyses and processing. Firstly, the methodology was based on the comparison between pre- and post-development catchment release scenarios and was applied to a case study catchment in the southern part of Catania. The study showed the need of careful consideration of the hydraulic invariance principle in land use planning practices. In particular, a set of flow release restrictions were determined for new areas of development, achieving the condition of unvaried flow peaks at the sub-catchment level, for different return periods of the storm-water event. Secondly, the methodology was applied to selected urban catchments in the centre of Avola. SWMM was used to track the quantity of runoff generated within each sub-catchment, and the flow rate and flow depth of water in each pipe in order to profile the system response to rainfall-runoff simulation. A dual-drainage approach was used to simulate the interaction between the minor and the major drainage systems and to obtain local flood characteristics to be mapped. Moreover, different effectiveness of selected SUDS measures were demonstrated in terms of improved water-flow regulation service and flood hazard mitigation, by comparing scenarios of pre- and post-implementation. Thesis discussion reflects the need for planning emphasis on mitigation and translating the understanding about risk, resilience and sustainable drainage into decisions via effective policy mechanisms. Suitable tools are needed to encourage a drainage-sensitive urban development and retrofitting.

This dissertation's urban vision looks at the environmental issues of land, water and the health of the people of Vanderbijlpark, all of which have been affected by heavy industry. The study sets out to address the deteriorating quality of the Vaal River's water and how this is affected by the tributaries feeding into it. This dissertation will focus on the remediation and monitoring of the contaminated water through an ecosystemic approach. The programme involves the removal of heavy metals from the industrial effluent from the surrounding heavy industry that flows into the Rietspruit Canal. The potential of micro-organisms, plants and insects will be explored as elements of a natural treatment system of the contaminated water. The site identified for the remediation processes is an abandoned parcel of land - a remnant of the natural landscape after urban sprawl. The algae and wetland treatment system will run through the facility, becoming the spine for the remediation process and movement through the facility. The production of silk, its uses and by-products will be integrated to support the overall system which treats the contaminated water. The facility aims to address the community's need to express their voice on environmental and health issues by integrating a community auditorium and exhibition space. The construction and materiality is grounded in the premise that the local companies will remain supportive and collaborative in the environmental intervention in the Rietspruit Canal system, into which they contribute considerable effluent. It will also be proposed that the local companies will fund and supply various steel products for the construction of the intervention. This will form part of the company's corporate social responsibility and a way of giving back to fringe communities affected by industry.
Die stedelike visie vir hierdie verhandeling fokus op die omgewingskwessies van grond, water en die gesondheid van die mense van Vanderbijlpark wie almal geraak word deur swaar nywerhede. Die studie spreek die verswakkende kwaliteit van die Vaalrivier se water aan en hoe dit geraak word deur sytakke wat daarin vloei. Die verhandeling sal fokus op wyses waarop besoedelde water deur middel van 'n ekosistemiese benadering herstel en gemonitor kan word. Die program behels die verwydering van swaar metale uit die industri?le uitvloeisel van die omliggende swaar nywerhede wat in die Rietspruit-kanaal vloei. Die potensiaal van mikro-organismes, plante en insekte as elemente van 'n natuurlike stelsel vir die behandeling van die besoedelde water, word ondersoek. Die terrein wat geidentifiseer is vir die herstelprosesse is 'n verlate stuk grond, 'n oorblyfsel van die natuurlike landskap na stadspreiding. Die stelsel vir die behandeling van alge en vleilandhabitatte sal deur die fasiliteit loop en die ruggraat van die herstelproses vorm. Die produksie van sy en die gebruike en neweprodukte daarvan sal geintegreer word om die totale sisteem wat die besoedelde water behandel, te ondersteun. Die fasiliteit het ten doel om die behoefte van die gemeenskap om hul stemme oor omgewings- en gesondheidskwessies te verhef, aan te spreek deur die gemeenskapsamfiteater en uitstalruimte te integreer. Die konstruksie en materialiteit is gegrond op die veronderstelling dat die grootste staalnywerheid, ArcelorMittal, ondersteunend en samewerkend sal wees ten opsigte van die omgewingsingryping in die Rietspruit-kanaalsisteem, waartoe hul aansienlike uitvloeisel bydra. Daar sal ook voorgestel word dat die swaar nywerhede die befondsing asook verskeie staalprodukte vir die oprigting van die fasiliteit sal verskaf. Dit sal deel uitmaak van die maatskappy se korporatiewe sosiale verantwoordelikheid en is 'n manier om aan gemeenskappe wat deur die industrie geaffekteer word, terug te gee.
Mini Dissertation (MArch (Prof))--University of Pretoria, 2016.
Architecture
MArch (Prof)
Unrestricted

Flooding over the last few years has become the most frequent and devastating of the natural disasters. This has accounted for approximately half of the death-rate and a third of economic losses as a result of weather-related events. Though these flooding events affect many cities across the globe, it is often the less fortunate who are disproportionately impacted by such events. There are many factors as to why this is the unfortunate case, with a high number of the underprivileged urban population finding themselves living in informal settlements. These settlements are often developed on environmentally-fragile land on steep sites or floodplains and lack the adequate waste and drainage systems that control the flow of water, further aggravating the flood risk within these areas. These uneven hardships are no different to Cape Town metropolitan region. Flooding has become an annual recurrence for the city during the wet winter months between May and September, with the informal settlements in the Cape Flats low-lying area bearing the brunt of this impact. The research therefore aims to explore how integrated flood control design within urban development can contribute to creating social and environmental sustainable interventions for flood resilience in informal settlements within the Cape Town municipality. One of the most important findings was the strong relation between waste as one of the largest contributors to the flooding events in these settlements, which became a key driver for investigation within the research. Kosovo informal settlement is one of the hardest hit communities during Cape Town’s high rainfall winter seasons and will used as the case study area for the research. The objective of the study is to investigate the existing condition and the involved stakeholders to develop well thought design strategies and toolbox for the municipality, planners, and residents. The design strategies and toolbox provides mechanisms to rethink flood prevention measures by shifting from creating barriers [interrupt], to mechanisms that engage with floodwater [interact] within a case study area. This research has attempted to position the community at the centre. Community participation and collaboration with key stakeholders will allow the residents to contribute with their local knowledge, experience and voices, sharing their views on the design solutions that are required to be integrated into their spaces.

Este estudo trata da caracterização hidromorfodinâmica de um setor paulista da planície fluvial meândrica do rio Ribeira de Iguape, abordando-se os três níveis da pesquisa geomorfológica de acordo com a concepção de HART (1986), a saber: (a) o nível descritivo da morfologia; (b) o nível descritivo dos materiais superficiais e solos; e (c) o nível analítico interpretativo dos processos, que, no caso, são hidrodinâmicos. Os resultados possibilitaram compreensão da hidromorfodinâmica das planícies fluviais meândricas em ambientes tropicais úmidos e, principalmente, da planície de inundação, podendo servir de subsídios no planejamento físico territorial regional, tendo em vista a importância da ocupação humana dentro desses setores.
The objective of this research is the hydromorphodynamic characterization of the Paulista River Ribeira de Iguape sector, approaching three levels of the geomorphology research according HART (1986), to know: (a) the morphology descriptive level; (b) the superficial materials and ground descriptive level; and (c) the processes interpretation analytical level, or hydrodynamic processes. With these surveys and systematization was possible the partially understanding humid tropical environments hidromorphodynamics trends and, mainly, of the flooding plain, which can be used in the regional territorial physical planning, in view of the importance of the occupation human being on these sectors.

O sistema fluvial meândrico do Rio Pinheiros em São Paulo (SP) tem passado por muitas mudanças geomorfológicas devido a intervenções antrópicas decorrentes da urbanização. A hipótese motivadora é a de que estas mudanças apresentam magnitudes maiores ou equivalentes àquelas registradas em condições naturais ou não urbanizadas. A pesquisa foi realizada por meio de técnicas oriundas da geomorfologia antrópica e histórica, do mapeamento geomorfológico e da análise de geoindicadores de mudanças nas formas da Terra, nos materiais superficiais e nos processos. Por meio da elaboração de três cartas geomorfológicas na escala de 1:25.000 representativas de distintos estágios de perturbação antrópica (pré-perturbação, perturbação ativa e pós-perturbação), foi possível identificar e dimensionar as mudanças históricas no sistema hidromorfológico desde 1930. Os resultados revelaram a elevada magnitude e alta eficiência das intervenções humanas diretas e indiretas nas morfologias e processos hidromorfológicos. Mudanças esperadas para ocorrer em condições naturais ou não urbanas em intervalos de 1 em 10³ a 1 em 104 anos podem se tornar eventos mais frequentes e instantâneos devido à urbanização (1 em 100 a 1 em 10² anos), fazendo as fontes históricas bastante adequadas para a sua identificação. Em apenas 21 anos, o canal meândrico pré-urbano foi substituído por um canal artificial retilíneo, seu comprimento foi reduzido em 44,9% e sua largura foi aumentada em 184,9%. O canal anterior transportava sedimentos finos e matéria orgânica num fluxo dágua constante para jusante. O canal atual tem uma vazão baixa e controlada artificialmente por estruturas de engenharia, que podem reverter o fluxo dágua para montante, fazendo com que o antigo sistema fluvial fosse transformado em um sistema próximo ao lacustre. A maioria dos sedimentos, matéria orgânica e poluentes é depositada no leito do canal, gerando problemas ambientais e de assoreamento. Nos últimos 80 anos, a antiga planície de inundação foi suprimida e novos níveis de terraços foram criados pela atividade humana, especialmente por aterros, cujo volume foi estimado em 16,28x106 m3. As inundações por extravasamento do canal foram reduzidas por causa das estruturas de controle de cheias, e ficam restritas às suas margens imediatas. Entretanto, a capacidade de atenuação das inundações da planície de inundação e baixos terraços foi perdida, e a frequência e magnitude das inundações foram potencializadas por causa da rede de drenagem urbana deficiente, da obstrução por aterros e pela construção de avenidas de fundo de vale nos rios afluentes. Compreender mudanças de tal magnitude auxilia na gestão dos rios e planícies urbanas, nos levantamentos geotécnicos e na identificação das possibilidades de recuperação ambiental, onde as funções ecológicas, hidrológicas e sociais dos sistemas fluviais devem ser restauradas.
The urbanised meandering fluvial system of River Pinheiros in Sao Paulo, Brazil, has undergone many geomorphological changes due to human interventions during the urban development. The central hypothesis is that geomorphological changes related to urbanisation over a fluvial plain in tropical humid environment present magnitudes higher than, or similar to, natural or non-urban systems. These changes can be explained by using such techniques as anthropic and historical geomorphology, geomorphological mapping, and geoindicators of change in landforms, materials and processes. Three 1:25,000 geomorphological maps of representative stages of intervention (pre-disturbance, active disturbance and post-disturbance) helped to establish, measure and compare historical changes in the hydromorphological system since 1930. The results revealed the great magnitude and high efficiency of direct and indirect human interventions on fluvial landforms and hydromorphological processes. Changes that might be expected to occur at intervals of 1 in 10³ to 1 in 104 years in natural conditions can become much more frequent events (1 in 100 to 1 in 10² years) due to urbanisation, making the historical sources quite suitable for the identification of these modifications. In just 21 years the pre-urban meandering channel was replaced by a straight and artificial canal, with the length being reduced by 44.9%, the width being increased by 184.9%. The previous fluvial channel carried fine sediments and organic matter in a constant downstream water flow. The current canal has the water flow artificially controlled by engineering structures which can be reversed upstream and, nowadays, behaves as a series of lakes with negligible flow. Most of sediments, organic matter and pollutants are deposited in the canal bed, generating siltation and environmental problems. During the last 80 years the previous floodplain level was eliminated and new terrace levels were created by human activity, particularly by landfills whose volume was estimated to be 16.28x106 m3. Floods by channel overflow were reduced by the engineering structures and are restricted to the nearest banks. However, the flood attenuation capacity of the floodplain and lower terraces was lost and the flood frequency and magnitude was enhanced due to deficient urban drainage, landfill blockage and where the tributaries were recovered by roads. Understanding changes of this magnitude can assist in river and flood management in urban areas, in geotechnical surveys and in the landscape reclamation.

La gestió de l'aigua residual és una tasca complexa. Hi ha moltes substàncies contaminants conegudes però encara moltes per conèixer, i el seu efecte individual o col·lgectiu és difícil de predir. La identificació i avaluació dels impactes ambientals resultants de la interacció entre els sistemes naturals i socials és un assumpte multicriteri. Els gestors ambientals necessiten eines de suport pels seus diagnòstics per tal de solucionar problemes ambientals.
Les contribucions d'aquest treball de recerca són dobles: primer, proposar l'ús d'un enfoc basat en la modelització amb agents per tal de conceptualitzar i integrar tots els elements que estan directament o indirectament involucrats en la gestió de l'aigua residual. Segon, proposar un marc basat en l'argumentació amb l'objectiu de permetre als agents raonar efectivament. La tesi conté alguns exemples reals per tal de mostrar com un marc basat amb agents que argumenten pot suportar diferents interessos i diferents perspectives. Conseqüentment, pot ajudar a construir un diàleg més informat i efectiu i per tant descriure millor les interaccions entre els agents. En aquest document es descriu primer el context estudiat, escalant el problema global de la gestió de la conca fluvial a la gestiódel sistema urbà d'aigües residuals, concretament l'escenari dels abocaments industrials. A continuació, s'analitza el sistema mitjançant la descripció d'agents que interaccionen. Finalment, es descriuen alguns prototips capaços de raonar i deliberar, basats en la lògica no monòtona i en un llenguatge declaratiu (answer set programming).
És important remarcar que aquesta tesi enllaça dues disciplines: l'enginyeria ambiental (concretament l'àrea de la gestió de les aigües residuals) i les ciències de la computació (concretament l'àrea de la intel·ligència artificial), contribuint així a la multidisciplinarietat requerida per fer front al problema estudiat. L'enginyeria ambiental ens proporciona el coneixement del domini mentre que les ciències de la computació ens permeten estructurar i especificar aquest coneixement.
Wastewater management is a very complex task. There is a high number of known and an increasing number of unknown pollutants whose individual and collective effects are very difficult to predict. Identifying and evaluating the impacts of environmental problems resulting from the interactions between our social system and its natural environment is a multifaceted critical issue. Environmental managers require tools to support their diagnoses for solving these problems. The contributions of this research work are twofold: first, to propose the use of an agent-based modelling approach in order to conceptualize and integrate all elements that are directly or indirectly involved in wastewater management. Second, to propose a framework based on argumentation that allows to reason effectively. The thesis provide some real examples to show that an agent-based argumentation framework can deal with multiple interests and different agents' perspectives and goals. This help to build a more effective and informed dialog in order to better describe the interaction between agents. In this document we first describe the context under study, scaling down the global river basins system to the urban wastewater systems and giving some more details for the specific scenario of industrial wastewater discharges. Then, we analyze the system in describing intelligent agents that interact. Finally, we propose some reasoning and deliberation prototypes by using an argumentation framework founded on non-monotonic logics (i.e. permitting to learn things that were previously not known) and the answer set programming specification language (i.e. a declarative programming language). It is important to remark that this thesis links two disciplines: environmental engineering (specifically the area of wastewater management) and computer science (specifically the area of artificial intelligence), contributing to the required multidsciplinarity needed to confront the complexity of the problem under study. From environmental engineering we obtain the domain knowledge whereas the computer science field permits us to structure and specify this knowledge.

The severity and frequency of flooding-related catastrophes are increasing, and lands adjacent to rivers that were formerly the hub for city growth and commerce now face constant threats of flooding. As flood risks have become more at the forefront of legislative consciousness, with governments increasing flood-protection and mitigation measures for flood-prone areas, landowners within such areas are left with little support and direction for their lands. In exploring the issues facing landowners within flood-prone lands, this practicum focuses on whether governments should be directly involved in finding solutions for landowners to ensure a situation where both private landowners and governments benefit. The research concludes that development within flood-prone areas should be avoided, and that municipalities should, given adequate capacity and ability, relocate existing residents from flood-prone areas to repurpose the area for flood-mitigation measures. The research recommends that the City of Brandon become a member, and participate in the Red River Basin Commission, while also exploring opportunities to play a leadership role in the implementation of a similar commission for the Assiniboine River Basin.
February 2017

abstract: A model is presented for real-time, river-reservoir operation systems. It epitomizes forward-thinking and efficient approaches to reservoir operations during flooding events. The optimization/simulation includes five major components. The components are a mix of hydrologic and hydraulic modeling, short-term rainfall forecasting, and optimization and reservoir operation models. The optimization/simulation model is designed for ultimate accessibility and efficiency. The optimization model uses the meta-heuristic approach, which has the capability to simultaneously search for multiple optimal solutions. The dynamics of the river are simulated by applying an unsteady flow-routing method. The rainfall-runoff simulation uses the National Weather Service NexRad gridded rainfall data, since it provides critical information regarding real storm events. The short-term rainfall-forecasting model utilizes a stochastic method. The reservoir-operation is simulated by a mass-balance approach. The optimization/simulation model offers more possible optimal solutions by using the Genetic Algorithm approach as opposed to traditional gradient methods that can only compute one optimal solution at a time. The optimization/simulation was developed for the 2010 flood event that occurred in the Cumberland River basin in Nashville, Tennessee. It revealed that the reservoir upstream of Nashville was more contained and that an optimal gate release schedule could have significantly decreased the floodwater levels in downtown Nashville. The model is for demonstrative purposes only but is perfectly suitable for real-world application.
Dissertation/Thesis
Doctoral Dissertation Civil Engineering 2015

In 2013, the "EU Strategy in adaptation to climate change" adopted by the European Commission stated the need of adaptation to climate impacts of European territories, including coastal areas. In fact, these areas are characterized by a higher concentration of buildings and people in comparison to inland areas. Furthermore, economic assets within 500 meters from the coastline have a value between €500 and €1,000 billion (EEA, 2016). Due to their several resources and the high degree of accessibility, these areas are very attractive for people and, hence, their population growth is expected to increase in the future (Neumann et al., 2015). Therefore, these characteristics make coastal cities particularly vulnerable to the impacts of climate change. One of the forecasted impacts of climate change in these areas is the increase of coastal floods due to rising sea level and storm surges. In this context, urban planning plays a key role in urban adaptation. However, even though the interest in this topic is increasing, operative support and tools for planning urban adaptation for cities are in short supply, especially for coastal cities. To date, urban adaptation has been mainly based on the concept of vulnerability and several vulnerability indices have been developed for supporting decision makers in the adaptation process of coastal areas, especially on the territorial level, grounding on a sectoral perspective. As a consequence, the adoption of this approach does not allow to take into account the complexity of the coastal urban system and, thus, all the features and their relationships that can affect the effectiveness of the urban measures to implement in the process of urban adaptation. Based on these observations, the purpose of this research was the development of a new decision support tool that allows the most suitable urban actions to be identified for increasing the capacity of cities to deal with coastal flooding events due to future rising sea level and storm surges. Besides the use of the most innovative GIS-based technologies, one of the novelties introduced with this work was the adoption of the holistic-system approach for the tool development, such as in the case of the definition of the new composite index based on the more holistic concept of urban resilience. For what concerns the development of the GIS-based tool, a four-phase methodology was defined. The first step was the definition and development of a novel composite index for a quantitative evaluation of the “urban coastal resilience” on the local level, named Coastal Resilience Index (or CoRI), by the Analytic Hierarchy Process (AHP) (Saaty, 1980), supported by the Delphi Method. In particular, the CoRI index allows the identification of four resilience levels (high, medium-high, medium-low and low). In the second step, since the urban adaptation measures should be defined in relation to physical and functional characteristics of the urban context, a classification of urban coastal areas was introduced, by specifying Urban Coastal Units (UCUs) depending on their urban density and land use. Considering the CoRI levels and the UCU classification and according to the coastal adaptation approaches defined by the IPCC (Nicholls et al., 2007), in the third phase, four classes of Urban Adaptation Actions were defined. In detail, a matrix that puts in relation the Urban Adaptation Actions classes with UCUs and CoRI levels has been developed. In relation to these three main phases and considering the potentialities of GIS applications in urban planning, in the last phase, a design workflow for developing the GIS-based tool was defined. Thanks to this workflow, the GIS-based tool was implemented and applied to a study area in the city of Naples. In particular, the identification of the potential coastal floodplains of Naples was useful for selecting the study area that includes five neighbourhoods - Barra, Mercato, Industrial Zone, Pendino and San Giovanni a Teduccio - localized in the eastern part of the city. Hence, the input data of the area chosen for the tool's implementation were collected. According to the methodology aforementioned, the GIS-based tool was realized considering three toolboxes: the “Coastal Resilience Index Tools” toolbox, the “Urban Coastal Units Tools” toolbox and, finally, the “Urban Adaptation Actions Tools” toolbox. From the application of the GIS-based tool to the study area, the main findings were the following ones. About the CoRI, the study area is characterized by a high presence of urban areas with medium-low resilience levels (61% of the study area) and by the absence of urban areas with high resilience levels. Concerning the UCU, the urban area is characterized by a high physical and functional complexity of the urban area. Therefore, the majority of the study area is classified as UCU 1 (i.e. high-density and mix-used developments) and UCU 2 (i.e. mono-functional zones, transport infrastructure, public facilities), while the absence of natural areas is noted. Regarding the identification of the Urban Adaptation Actions, all the UCUs need to enhance their resilience level through the implementation of fitting urban measures due to the absence of urban areas characterized by high resilience levels and the high urbanization degree of the study area. In particular, in the majority of the area (about 61%), it is necessary to implement a mix of “hardware” and “software” measures. Therefore, urban transformations should be addressed towards the realization or improvement of protection infrastructure systems, the use of resilient design standards at building scale and the reduction of land-use intensity through the delocalization of critical facilities from the coastline. From an urban planning perspective, the application of the GIS-based tool to the study area in Naples highlights how the urban layout and spatial organization can affect the urban capacity to deal with coastal flooding. Indicators that compose the CoRI enable the in-depth study of urban contexts, and identify areas where there are major shortcomings in terms of urban resilience. Whereas the Urban Coastal Units classification enables the categorization of coastal areas in relation to their land use and land-use intensity in order to better identify the most appropriate “palette” of urban adaptation actions to implement. The identification of a set of urban actions for different urban typologies can be useful for not only defining and programming new urban transformations but also for allowing decision-makers to monetize possible interventions to carry out. In conclusion, urban transformations will be more and more necessary in order to adapt urban areas to future impacts due to climate change. Therefore, in order to better deal with the forthcoming climate change impacts on cities, the novel methodology provided in this study sets the framework for the development of new urban planning tools capable to cope with other climate impacts and, eventually, for their integration in order to develop a comprehensive tool for urban adaptation to different possible impacts of climate change (Wardekker et al., 2010).

Over the last few decades, the world has witnessed rapid urbanisation. One of the many complex problems resulting from increased urbanisation is related to management of stormwater from developed areas. If stormwater is not managed properly, it may lead to flooding of urban areas, and deterioration of water quality in rivers and receiving waters. Urban drainage systems are used to manage urban stormwater. For design of effective and economic urban drainage systems, it is important to estimate the design flows accurately. Many computer based mathematical models have been developed to study catchment runoff (or flows) in urban environments. These models may be used in different stages of the projects such as screening, planning, design and operation. Each stage may require a different model, although some models can be used for several of these stages. A customer survey was conducted in May 1997 to study the current practice in Victoria (Australia) on stormwater drainage design and analysis, as part of this thesis. The survey was restricted to city/shire councils and consultants, who are engaged in design and analysis of urban drainage systems. The results of the survey showed that 95% of respondents used the Statistical Rational method. Also, it was revealed that most respondents were reluctant to use stormwater drainage computer models, since there were no adequate guidelines and information available to use them especially for ungauged catchments. According to 5% of the respondents, who used models, ILSAX was the most widely used stormwater drainage computer model in Victoria. The 1987 edition of the Australian Rainfall-Runoff (ARR87) suggests the ILSAX model as one of the computer models that can be used for stormwater drainage design and analysis. Due to these reasons, the ILSAX model was used in this study in an attempt to produce further guidance to users in development and calibration of ILSAX models of urban drainage systems. In order to use the ILSAX model, it is necessary to estimate the model parameters for catchments under consideration. The model parameters include loss model parameters (i.e. infiltration and depression storage parameters) and other parameters related to the catchment (such as percent imperviousness, soil cover and conveyance system parameters). Some of these parameters can be estimated from available maps and drawings of the catchment. The ideal method to determine these parameters (which cannot be reliably determined from available maps and drawings) is through calibration of these models using observed rainfall and runoff data. However, only few urban catchments are monitored for rainfall and runoff, and therefore calibration can be done only for these catchments. At present, there are no clear guidelines to estimate the model parameters for ungauged catchments where no rainfall-runoff data are available. In this PhD project, first the ILSAX model was calibrated for some gauged urban catchments. From the results of calibration of these catchments, regression equations were developed to estimate some model parameters for use in gauged and ungauged urban stormwater catchments. Before calibrating the ILSAX model for gauged catchments, a detailed study was conducted to; - select the most appropriate modelling option (out of many available in ILSAX) for modelling various urban drainage processes, - study the sensitivity of model parameters on simulated storm hydrographs, and - study the effect of catchment subdivision on storm hydrographs. This detailed study was conducted using two typical urban catchments (i.e. one 'small' and one 'large') in Melbourne metropolitan area (Victoria) considering four design storms of different average recurrence intervals (ARI). Three storms with ARI of 1, 10 and 100 years, and one with ARI greater than 100 years were considered in the study. The results obtained from this detailed study were subsequently used in model calibration of the study catchments. The results showed that the runoff volume of 'large' storm events was more sensitive to the antecedent moisture condition and the soil curve number (which determines soil infiltration) and less sensitive to the pervious and impervious area depression storages. However, for 'small' storm events, the runoff volume was sensitive to the impervious area depression storage. The peak discharge was sensitive to pipe roughness, pit choke factor, pit capacity parameters and gutter characteristics for both 'small' and 'large' storm events. The results also showed that the storm hydrograph was sensitive to the catchment subdivision. The accuracy of rainfall-runoff modelling can be adversely influenced by erroneous input data. Therefore, the selection of accurate input data is crucial for development of reliable and predictive models. In this research project, a number of data analysis techniques were used to select good quality data for model calibration. For calibration of model parameters, parameter optimisation was preferred to the trial and error visual comparison of observed and modelled output responses, due to subjectivity and time-consuming nature of the latter approach. It was also preferred in this study, since the model parameters obtained from calibration were used in the development of regional equations for use in gauged and ungauged catchments. Therefore, it was necessary to have a standard method which can be repeated, and produced the same result when the method is applied at different times for a catchment. An optimisation procedure was developed in this thesis, to estimate the model parameters of ILSAX. The procedure was designed to produce the 'best' set of model parameters that considered several storm events simultaneously. The PEST computer software program was used for the parameter optimisation. According to this procedure, the impervious area parameters can be obtained from frequent 'small' storm events, while the pervious area parameters can be obtained from less-frequent 'large' storm events. Twenty two urban catchments in the Melbourne metropolitan area (Victoria) were considered in the model parameter optimisation. Several 'small' and 'large' storm events were considered for each catchment. However, it was found during the analysis that the selected 'large' storm events did not produce any pervious area runoff, and therefore it was not possible to estimate the pervious area parameters for these catchments. The Giralang urban catchment in Canberra (Australia) was then selected to demonstrate the optimisation procedure for estimating both impervious and pervious area parameters, since data on 'small' and 'large' storm events were available for this catchment. The calibration results were verified using different sets of storm events, which were not used in the calibration, for all catchments. The optimised model parameters obtained for each catchment were able to produce hydrographs similar to the observed hydrographs, during verification. The impervious area parameters obtained from optimisation agreed well with the information obtained from other sources such as areal photographs, site visits and published literature. Similarly, the pervious area parameters obtained for the Giralang catchment agreed well with the values given in the published literature. If ILSAX is to be used for ungauged drainage systems for which no storm data are available, then the model parameters have to be estimated by some other means. One method is to estimate them through regional equations, if available. These regional equations generally relate the model parameters to measurable catchment properties. In this study, analyses were conducted to develop such regional equations for use in ungauged residential urban catchments in the Melbourne metropolitan area. The Melbourne metropolitan area was considered as one hydrologically homogeneous group, since the urban development is similar in the area. The equations were developed for the land-use parameters of directly connected impervious area percentage (DCIA) and supplementary area percentage (SA), and the directly connected impervious area depression storage (DSi). Several influential catchment parameters such as catchment area, catchment slope, distance from the Central Business District to the catchment and household density were considered as independent variables in these regional equations. A regional equation was developed for DCIA as a function of the household density. A similar equation was also developed to determine SA as a function of household density. DCIA was obtained from the model parameter optimisation using rainfall-runoff data (i.e. calibration), while SA and household density were obtained from the available drawings and field visits. These two equations showed a very good correlation with household density and therefore, DCIA and SA can be estimated accurately using these two equations. The city/shire councils generally have information on the household density in already developed urban areas and therefore, these two equations can be used to estimate DCIA and SA for these areas. For new catchments, these equations can be used to estimate DCIA and SA based on the proposed household density. The directly connected impervious area depression storage (DSi) is the only ILSAX model loss parameter that was obtained from the calibration, and this is the loss parameter that is more sensitive for 'small' storm events of the urban drainage catchments. A regional equation was attempted for this parameter by relating with the catchment slope, since the catchment slope was found to have some correlation with DSi according to past studies. However, the results in this study did not show a correlation between these two variables. Therefore, based on the results of this study, a range of 0 - 1 mm was recommended for DSi. Because of the recommended range for DSi, the sensitivity of DSi against DCIA was revisited and found that DSi was less sensitive compared to DCIA, in simulating the peak discharge and time to peak discharge for both 'small' and 'large' storm events. However, there is a little impact for runoff volume and hydrograph shape for 'small' storm events. Therefore, defining a range for DSi is justified for modelling purposes and the user can choose a suitable value within this range from engineering judgement.

Climate change is projected to increase the intensity and frequency of storm events that would increase flooding hazards. Urbanization associated with land use and land cover change has altered hydrological cycles by increasing stormwater runoff, reducing baseflow and increasing flooding hazards. Combined urbanization and climate change impacts on long-term riparian flooding during future growth are likely to affect more socially vulnerable populations. Growth strategies and green infrastructure are critical planning interventions for minimizing urbanization impacts and mitigating flooding hazards. Within the social-ecological systems planning framework, this empirical research evaluated the effects of planning interventions (infill development and stormwater detention) through a risk assessment in three studies. First, a climate sensitivity study using SWAT modeling was conducted for building a long-term flooding hazard index (HI) and determining climate change impact scenarios. A Social Vulnerability Index (SoVI) was constructed using socio-economic variables and statistical methods. Subsequently, the long-term climate change-induced flooding risk index (RI) was formulated by multiplying HI and SoVI. Second, growth strategies in four future growth scenarios developed through the BMA ULTRA-ex project were evaluated through land use change input in SWAT modeling and under climate change impact scenarios for the effects on the risk indices. Third, detention under climate sensitivity study using SWAT modeling was investigated in relation to long-term flooding hazard indices. The results illustrated that increasing temperature decreases HI while increasing precipitation change and land use change would increase HI. In addition, there is a relationship between climate change and growth scenarios which illustrates a potential threshold when the impacts from land use and land cover change diminished under the High impact climate change scenario. Moreover, spatial analysis revealed no correlation between HI and SoVI in their current conditions. Nevertheless, the Current Trends scenario has planned to allocate more people living in the long-term climate change-induced flooding risk hotspots. Finally, the results of using 3% of the watershed area currently available for detention in the model revealed that a projected range of 0 to 8% watershed area would be required to mitigate climate change-induced flooding hazards to the current climate conditions. This research has demonstrated the value of using empirical study on a local scale in order to understand the place-based and watershed-specific flooding risks under linked social-ecological dynamics. The outcomes of evaluating planning interventions are critical to inform policy-makers and practitioners for setting climate change parameters in seeking innovations in planning policy and practices through a transdisciplinary participatory planning process. Subsequently, communities are able to set priorities for allocating resources in order to enhance people's livelihoods and invest in green infrastructure for building communities toward resilience and sustainability.

Increasing global mean temperature or global warming has the potential to affect the hydrologic cycle. In the 21st century, according to the UN Intergovernmental Panel on Climate Change (IPCC), alterations in the frequency and magnitude of high intensity rainfall events are very likely. Increasing trend of urbanization across the globe is also noticeable, simultaneously. These changes will have a great impact on water infrastructure as well as environment in urban areas. One of the impacts may be the increase in frequency and extent of flooding. India, in the recent years, has witnessed a number of urban floods that have resulted in huge economic losses, an instance being the flooding of Mumbai in July, 2005. To prevent catastrophic damages due to floods, it has become increasingly important to understand the likely changes in extreme rainfall in future, its effect on the urban drainage system, and the measures that can be taken to prevent or reduce the damage due to floods. Reliable estimation of future design rainfall intensity accounting for uncertainties due to climate change is an important research issue. In this context, rainfall intensity-duration-frequency (IDF) relationships are one of the most extensively used hydrologic tools in planning, design and operation of various drainage related infrastructures in urban areas. There is, thus, a need for a study that investigates the potential effects of climate change on IDF relationships. The main aim of the research reported in this thesis is to investigate the effect of climate change on Intensity-Duration-Frequency relationship in an urban area. The rainfall in Bangalore City is used as a case study to demonstrate the applications of the methodologies developed in the research Ahead of studying the future changes, it is essential to investigate the signature of changes in the observed hydrological and climatological data series. Initially, the yearly mean temperature records are studied to find out the signature of global warming. It is observed that the temperature of Bangalore City shows an evidence of warming trend at a statistical confidence level of 99.9 %, and that warming effect is visible in terms of increase of minimum temperature at a rate higher than that of maximum temperature. Interdependence studies between temperature and extreme rainfall reveal that up to a certain range, increase in temperature intensifies short term rainfall intensities at a rate more than the average rainfall. From these two findings, it is clear that short duration rainfall intensities may intensify in the future due to global warming and urban heat island effect. The possible urbanization signatures in the extreme rainfall in terms of intensification in the evening and weekends are also inferred, although inconclusively. The IDF relationships are developed with historical data and changes in the long term daily rainfall extreme characteristics are studied. Multidecedal oscillations in the daily rainfall extreme series are also examined. Further, non-parametric trend analyses of various indices of extreme rainfall are carried out to confirm that there is a trend of increase in extreme rainfall amount and frequency, and therefore it is essential to the study the effects of climate change on the IDF relationships of the Bangalore City. Estimation of future changes in rainfall at hydrological scale generally relies on simulations of future climate provided by Global Climate Models (GCMs). Due to spatial and temporal resolution mismatch, GCM results need to be downscaled to get the information at station scale and at time resolutions necessary in the context of urban flooding. The downscaling of extreme rainfall characteristics in an urban station scale pose the following challenges: (1) downscaling methodology should be efficient enough to simulate rainfall at the tail of rainfall distribution (e.g., annual maximum rainfall), (2) downscaling at hourly or up to a few minutes temporal resolution is required, and (3) various uncertainties such as GCM uncertainties, future scenario uncertainties and uncertainties due to various statistical methodologies need to be addressed. For overcoming the first challenge, a stochastic rainfall generator is developed for spatial downscaling of GCM precipitation flux information to station scale to get the daily annual maximum rainfall series (AMRS). Although Regional Climate Models (RCMs) are meant to simulate precipitation at regional scales, they fail to simulate extreme events accurately. Transfer function based methods and weather typing techniques are also generally inefficient in simulating the extreme events. Due to its stochastic nature, rainfall generator is better suited for extreme event generation. An algorithm for stochastic simulation of rainfall, which simulates both the mean and extreme rainfall satisfactorily, is developed in the thesis and used for future projection of rainfall by perturbing the parameters of the rainfall generator for the future time periods. In this study, instead of using the customary two states (rain/dry) Markov chain, a three state hybrid Markov chain is developed. The three states used in the Markov chain are: dry day, moderate rain day and heavy rain day. The model first decides whether a day is dry or rainy, like the traditional weather generator (WGEN) using two transition probabilities, probabilities of a rain day following a dry day (P01), and a rain day following a rain day (P11). Then, the state of a rain day is further classified as a moderate rain day or a heavy rain day. For this purpose, rainfall above 90th percentile value of the non-zero precipitation distribution is termed as a heavy rain day. The state of a day is assigned based on transition probabilities (probabilities of a rain day following a dry day (P01), and a rain day following a rain day (P11)) and a uniform random number. The rainfall amount is generated by Monte Carlo method for the moderate and heavy rain days separately. Two different gamma distributions are fitted for the moderate and heavy rain days. Segregating the rain days into two different classes improves the process of generation of extreme rainfall. For overcoming the second challenge, i.e. requirement of temporal scales, the daily scale IDF ordinates are disaggregated into hourly and sub-hourly durations. Disaggregating continuous rainfall time series at sub-hourly scale requires continuous rainfall data at a fine scale (15 minute), which is not available for most of the Indian rain gauge stations. Hence, scale invariance properties of extreme rainfall time series over various rainfall durations are investigated through scaling behavior of the non-central moments (NCMs) of generalized extreme value (GEV) distribution. The scale invariance properties of extreme rainfall time series are then used to disaggregate the distributional properties of daily rainfall to hourly and sub-hourly scale. Assuming the scaling relationships as stationary, future sub-hourly and hourly IDF relationships are developed. Uncertainties associated with the climate change impacts arise due to existence of several GCMs developed by different institutes across the globe, climate simulations available for different representative concentration pathway (RCP) scenarios, and the diverse statistical techniques available for downscaling. Downscaled output from a single GCM with a single emission scenario represents only a single trajectory of all possible future climate realizations and cannot be representative of the full extent of climate change. Therefore, a comprehensive assessment of future projections should use the collective information from an ensemble of GCM simulations. In this study, 26 different GCMs and 4 RCP scenarios are taken into account to come up with a range of IDF curves at different future time periods. Reliability ensemble averaging (REA) method is used for obtaining weighted average from the ensemble of projections. Scenario uncertainty is not addressed in this study. Two different downscaling techniques (viz., delta change and stochastic rainfall generator) are used to assess the uncertainty due to downscaling techniques. From the results, it can be concluded that the delta change method under-estimated the extreme rainfall compared to the rainfall generator approach. This study also confirms that the delta change method is not suitable for impact studies related to changes in extreme events, similar to some earlier studies. Thus, mean IDF relationships for three different future extreme events, similar to some earlier studies. Thus, mean IDF relationships for three different future periods and four RCP scenarios are simulated using rainfall generator, scaling GEV method, and REA method. The results suggest that the shorter duration rainfall will invigorate more due to climate change. The change is likely to be in the range of 20% to 80%, in the rainfall intensities across all durations. Finally, future projected rainfall intensities are used to investigate the possible impact of climate change in the existing drainage system of the Challaghatta valley in the Bangalore City by running the Storm Water Management Model (SWMM) for historical period, and the best and the worst case scenario for three future time period of 2021–2050, 2051–2080 and 2071–2100. The results indicate that the existing drainage is inadequate for current condition as well as for future scenarios. The number of nodes flooded will increase as the time period increases, and a huge change in runoff volume is projected. The modifications of the drainage system are suggested by providing storage pond for storing the excess high speed runoff in order to restrict the width of the drain The main research contribution of this thesis thus comes from an analysis of trends of extreme rainfall in an urban area followed by projecting changes in the IDF relationships under climate change scenarios and quantifying uncertainties in the projections.

Increasing global mean temperature or global warming has the potential to affect the hydrologic cycle. In the 21st century, according to the UN Intergovernmental Panel on Climate Change (IPCC), alterations in the frequency and magnitude of high intensity rainfall events are very likely. Increasing trend of urbanization across the globe is also noticeable, simultaneously. These changes will have a great impact on water infrastructure as well as environment in urban areas. One of the impacts may be the increase in frequency and extent of flooding. India, in the recent years, has witnessed a number of urban floods that have resulted in huge economic losses, an instance being the flooding of Mumbai in July, 2005. To prevent catastrophic damages due to floods, it has become increasingly important to understand the likely changes in extreme rainfall in future, its effect on the urban drainage system, and the measures that can be taken to prevent or reduce the damage due to floods. Reliable estimation of future design rainfall intensity accounting for uncertainties due to climate change is an important research issue. In this context, rainfall intensity-duration-frequency (IDF) relationships are one of the most extensively used hydrologic tools in planning, design and operation of various drainage related infrastructures in urban areas. There is, thus, a need for a study that investigates the potential effects of climate change on IDF relationships. The main aim of the research reported in this thesis is to investigate the effect of climate change on Intensity-Duration-Frequency relationship in an urban area. The rainfall in Bangalore City is used as a case study to demonstrate the applications of the methodologies developed in the research Ahead of studying the future changes, it is essential to investigate the signature of changes in the observed hydrological and climatological data series. Initially, the yearly mean temperature records are studied to find out the signature of global warming. It is observed that the temperature of Bangalore City shows an evidence of warming trend at a statistical confidence level of 99.9 %, and that warming effect is visible in terms of increase of minimum temperature at a rate higher than that of maximum temperature. Interdependence studies between temperature and extreme rainfall reveal that up to a certain range, increase in temperature intensifies short term rainfall intensities at a rate more than the average rainfall. From these two findings, it is clear that short duration rainfall intensities may intensify in the future due to global warming and urban heat island effect. The possible urbanization signatures in the extreme rainfall in terms of intensification in the evening and weekends are also inferred, although inconclusively. The IDF relationships are developed with historical data and changes in the long term daily rainfall extreme characteristics are studied. Multidecedal oscillations in the daily rainfall extreme series are also examined. Further, non-parametric trend analyses of various indices of extreme rainfall are carried out to confirm that there is a trend of increase in extreme rainfall amount and frequency, and therefore it is essential to the study the effects of climate change on the IDF relationships of the Bangalore City. Estimation of future changes in rainfall at hydrological scale generally relies on simulations of future climate provided by Global Climate Models (GCMs). Due to spatial and temporal resolution mismatch, GCM results need to be downscaled to get the information at station scale and at time resolutions necessary in the context of urban flooding. The downscaling of extreme rainfall characteristics in an urban station scale pose the following challenges: (1) downscaling methodology should be efficient enough to simulate rainfall at the tail of rainfall distribution (e.g., annual maximum rainfall), (2) downscaling at hourly or up to a few minutes temporal resolution is required, and (3) various uncertainties such as GCM uncertainties, future scenario uncertainties and uncertainties due to various statistical methodologies need to be addressed. For overcoming the first challenge, a stochastic rainfall generator is developed for spatial downscaling of GCM precipitation flux information to station scale to get the daily annual maximum rainfall series (AMRS). Although Regional Climate Models (RCMs) are meant to simulate precipitation at regional scales, they fail to simulate extreme events accurately. Transfer function based methods and weather typing techniques are also generally inefficient in simulating the extreme events. Due to its stochastic nature, rainfall generator is better suited for extreme event generation. An algorithm for stochastic simulation of rainfall, which simulates both the mean and extreme rainfall satisfactorily, is developed in the thesis and used for future projection of rainfall by perturbing the parameters of the rainfall generator for the future time periods. In this study, instead of using the customary two states (rain/dry) Markov chain, a three state hybrid Markov chain is developed. The three states used in the Markov chain are: dry day, moderate rain day and heavy rain day. The model first decides whether a day is dry or rainy, like the traditional weather generator (WGEN) using two transition probabilities, probabilities of a rain day following a dry day (P01), and a rain day following a rain day (P11). Then, the state of a rain day is further classified as a moderate rain day or a heavy rain day. For this purpose, rainfall above 90th percentile value of the non-zero precipitation distribution is termed as a heavy rain day. The state of a day is assigned based on transition probabilities (probabilities of a rain day following a dry day (P01), and a rain day following a rain day (P11)) and a uniform random number. The rainfall amount is generated by Monte Carlo method for the moderate and heavy rain days separately. Two different gamma distributions are fitted for the moderate and heavy rain days. Segregating the rain days into two different classes improves the process of generation of extreme rainfall. For overcoming the second challenge, i.e. requirement of temporal scales, the daily scale IDF ordinates are disaggregated into hourly and sub-hourly durations. Disaggregating continuous rainfall time series at sub-hourly scale requires continuous rainfall data at a fine scale (15 minute), which is not available for most of the Indian rain gauge stations. Hence, scale invariance properties of extreme rainfall time series over various rainfall durations are investigated through scaling behavior of the non-central moments (NCMs) of generalized extreme value (GEV) distribution. The scale invariance properties of extreme rainfall time series are then used to disaggregate the distributional properties of daily rainfall to hourly and sub-hourly scale. Assuming the scaling relationships as stationary, future sub-hourly and hourly IDF relationships are developed. Uncertainties associated with the climate change impacts arise due to existence of several GCMs developed by different institutes across the globe, climate simulations available for different representative concentration pathway (RCP) scenarios, and the diverse statistical techniques available for downscaling. Downscaled output from a single GCM with a single emission scenario represents only a single trajectory of all possible future climate realizations and cannot be representative of the full extent of climate change. Therefore, a comprehensive assessment of future projections should use the collective information from an ensemble of GCM simulations. In this study, 26 different GCMs and 4 RCP scenarios are taken into account to come up with a range of IDF curves at different future time periods. Reliability ensemble averaging (REA) method is used for obtaining weighted average from the ensemble of projections. Scenario uncertainty is not addressed in this study. Two different downscaling techniques (viz., delta change and stochastic rainfall generator) are used to assess the uncertainty due to downscaling techniques. From the results, it can be concluded that the delta change method under-estimated the extreme rainfall compared to the rainfall generator approach. This study also confirms that the delta change method is not suitable for impact studies related to changes in extreme events, similar to some earlier studies. Thus, mean IDF relationships for three different future extreme events, similar to some earlier studies. Thus, mean IDF relationships for three different future periods and four RCP scenarios are simulated using rainfall generator, scaling GEV method, and REA method. The results suggest that the shorter duration rainfall will invigorate more due to climate change. The change is likely to be in the range of 20% to 80%, in the rainfall intensities across all durations. Finally, future projected rainfall intensities are used to investigate the possible impact of climate change in the existing drainage system of the Challaghatta valley in the Bangalore City by running the Storm Water Management Model (SWMM) for historical period, and the best and the worst case scenario for three future time period of 2021–2050, 2051–2080 and 2071–2100. The results indicate that the existing drainage is inadequate for current condition as well as for future scenarios. The number of nodes flooded will increase as the time period increases, and a huge change in runoff volume is projected. The modifications of the drainage system are suggested by providing storage pond for storing the excess high speed runoff in order to restrict the width of the drain The main research contribution of this thesis thus comes from an analysis of trends of extreme rainfall in an urban area followed by projecting changes in the IDF relationships under climate change scenarios and quantifying uncertainties in the projections.

In urbanized river basins, sanitary wastewater and urban runoff (non-sanitary water) from urban agglomerations drain to complex engineered networks, are treated at centralized wastewater treatment plants (WWTPs) and discharged to river networks. Discharge from multiple WWTPs distributed in urbanized river basins contributes to impairments of river water-quality and aquatic ecosystem integrity. The size and location of WWTPs are determined by spatial patterns of population in urban agglomerations within a river basin. Economic and engineering constraints determine the combination of wastewater treatment technologies used to meet required environmental regulatory standards for treated wastewater discharged to river networks. Thus, it is necessary to understand the natural-human-engineered networks as coupled systems, to characterize their interrelations, and to understand emergent spatiotemporal patterns and scaling of geochemical and ecological responses.

My PhD research involved data-model synthesis, using publicly available data and application of well-established network analysis/modeling synthesis approaches. I present the scope and specific subjects of my PhD project by employing the Drivers-Pressures-Status-Impacts-Responses (DPSIR) framework. The defined research scope is organized as three main themes: (1) River network and urban drainage networks (Foundation-Pathway of Pressures); (2) River network, human population, and WWTPs (Foundation-Drivers-Pathway of Pressures); and (3) Nutrient loads and their impacts at reach- and basin-scales (Pressures-Impacts).

Three inter-related research topics are: (1) the similarities and differences in scaling and topology of engineered urban drainage networks (UDNs) in two cities, and UDN evolution over decades; (2) the scaling and spatial organization of three attributes: human population (POP), population equivalents (PE; the aggregated population served by each WWTP), and the number/sizes of WWTPs using geo-referenced data for WWTPs in three large urbanized basins in Germany; and (3) the scaling of nutrient loads (P and N) discharged from ~845 WWTPs (five class-sizes) in urbanized Weser River basin in Germany, and likely water-quality impacts from point- and diffuse- nutrient sources.

I investigate the UDN scaling using two power-law scaling characteristics widely employed for river networks: (1) Hack’s law (length-area power-law relationship), and (2) exceedance probability distribution of upstream contributing area. For the smallest UDNs, length-area scales linearly, but power-law scaling emerges as the UDNs grow. While area-exceedance plots for river networks are abruptly truncated, those for UDNs display exponential tempering. The tempering parameter decreases as the UDNs grow, implying that the distribution evolves in time to resemble those for river networks. However, the power-law exponent for mature UDNs tends to be larger than the range reported for river networks. Differences in generative processes and engineering design constraints contribute to observed differences in the evolution of UDNs and river networks, including subnet heterogeneity and non-random branching.

In this study, I also examine the spatial patterns of POP, PE, and WWTPs from two perspectives by employing fractal river networks as structural platforms: spatial hierarchy (stream order) and patterns along longitudinal flow paths (width function). I propose three dimensionless scaling indices to quantify: (1) human settlement preferences by stream order, (2) non-sanitary flow contribution to total wastewater treated at WWTPs, and (3) degree of centralization in WWTPs locations. I select as case studies three large urbanized river basins (Weser, Elbe, and Rhine), home to about 70% of the population in Germany. Across the three river basins, the study shows scale-invariant distributions for each of the three attributes with stream order, quantified using extended Horton scaling ratios; a weak downstream clustering of POP in the three basins. Variations in PE clustering among different class-sizes of WWTPs reflect the size, number, and locations of urban agglomerations in these catchments.

WWTP effluents have impacts on hydrologic attributes and water quality of receiving river bodies at the reach- and basin-scales. I analyze the adverse impacts of WWTP discharges for the Weser River basin (Germany), at two steady river discharge conditions (median flow; low-flow). This study shows that significant variability in treated wastewater discharge within and among different five class-sizes WWTPs, and variability of river discharge within the stream order <3, contribute to large variations in capacity to dilute WWTP nutrient loads. For the median flow, reach-scale water quality impairment assessed by nutrient concentration is likely at 136 (~16%) locations for P and 15 locations (~2%) for N. About 90% of the impaired locations are the stream order < 3. At basin-scale analysis, considering in stream uptake resulted 225 (~27%) P-impaired streams, which was ~5% reduction from considering only dilution. This result suggests the dominant role of dilution in the Weser River basin. Under the low flow conditions, water quality impaired locations are likely double than the median flow status for the analyses. This study for the Weser River basin reveals that the role of in-stream uptake diminishes along the flow paths, while dilution in larger streams (4≤ stream order ≤7) minimizes the impact of WWTP loads.

Furthermore, I investigate eutrophication risk from spatially heterogeneous diffuse- and point-source P loads in the Weser River basin, using the basin-scale network model with in-stream losses (nutrient uptake).Considering long-term shifts in P loads for three representative periods, my analysis shows that P loads from diffuse-sources, mainly from agricultural areas, played a dominant role in contributing to eutrophication risk since 2000s, because of ~87% reduction of point-source P loads compared to 1980s through the implementation of the EU WFD. Nevertheless, point-sources discharged to smaller streams (stream order < 3) pose amplification effects on water quality impairment, consistent with the reach-scale analyses only for WWTPs effluents. Comparing to the long-term water quality monitoring data, I demonstrate that point-sources loads are the primary contributors for eutrophication in smaller streams, whereas diffuse-source loads mainly from agricultural areas address eutrophication in larger streams. The results are reflective of spatial patterns of WWTPs and land cover in the Weser River basin.

Through data-model synthesis, I identify the characteristics of the coupled natural (rivers) – humans – engineered (urban drainage infrastructure) systems (CNHES), inspired by analogy, coexistence, and causality across the coupled networks in urbanized river basins. The quantitative measures and the basin-scale network model presented in my PhD project could extend to other large urbanized basins for better understanding the spatial distribution patterns of the CNHES and the resultant impacts on river water-quality impairment.