Thesis (MA)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: This study was conducted in the Cuvelai Basin in Northern Namibia to assess vulnerability and socio-economic impacts of flooding on local residents, and to suggest ways to counteract the consequences of flooding in rural areas of the Basin. This followed severe flooding in 2009, 2011 and 2012. These combined flooding episodes had a substantial impact on local residents and the Namibian economy, with estimated losses of approximately US$136.4 million (NAD1364 million) in direct damage and US$78.2 million (NAD780 million) in indirect losses. The consequences of flooding amounted to ~1% of the country’s 2009 Gross Domestic Product (GDP). Rural residents in the Cuvelai Basin live predominantly on small farm holdings (‘ekove’) allocated by local village leadership, and depend heavily on subsistence farming for their livelihoods. Since higher-lying ground with soil best suited for crop production becomes scarcer, residents are allocated land in low-lying areas which are smaller and more susceptible to floods. The destruction of crops, farm and grazing land, trees and livestock, by floods and similar disasters is of a huge concern. The study sought to assess the impacts of flooding, geographical or physical circumstances that place residents at risk, and socio-economic conditions that lead to vulnerability. The study also attempted to assess whether traditional leaders (headmen) and village residents can use flood risk maps to create plans to reduce flood vulnerability. Over the past flood years, initiatives by the government to cope with floods have been response (relief), short-term and heavily donor dependent. To cope with floods and agro-climatic changes in their basin, rural residents have evolved their practices, some of which are traditional, to help lessen the impacts of floods on their livelihoods. Unfortunately such knowledge is not fully acknowledged by policy, decision makers and disaster risk managers. As a result of this knowledge gap, the study’s objective of compiling these practices, serves as a means to document localized traditional flood response, mitigation and adaptive measures. Moreover, the study will suggest contemporary adaptive measures as recommended by the local rural residents. Residents in 314 households were interviewed during August to November 2012. The households were selected following recommendations by village headmen, and consisted of 273 flooded homes, 42 village leaders, and 35 homes that were not flooded from 45 randomly selected villages. The qualitative data was captured, pre-coded, processed and analysed in Microsoft Excel, SPSS and STATISTICA to derive descriptive and inferential statistics. Following consultations with village headmen and residents, recommendations were made on practical adaptive strategies to flooding. The study found that there is a need to foster community level participation, buy-in and involvement in disaster risk management strategies in order to reduce the gap between technical early warning mechanisms and indigenous knowledge. Results revealed that households with coinciding socio-economic and geographic vulnerability are heavily impacted by flood disasters. However, these two vulnerabilities are not directly proportional to each other. Other vulnerable groups in society were outlined and structural and non-structural mitigation and preparedness measures at household level were recommended by the residents. It is the study’s intention that this will assist in strengthening local residents adaptive capabilities during events of flooding, thereby mitigating their impacts. The project’s intention of documenting this technical and indigenous knowledge, will serve as a knowledge base that can be compiled and integrated into an effective village friendly flood early warning system. It is further hoped that this initiative will garner support at the policy level and contribute to the prioritization of flood response to pending disasters being placed at the centre of development planning and execution. / AFRIKAANSE OPSOMMING: Hierdie studie is uitgevoer in die Cuvelai-opvangsgebied om die kwesbaarheid en sosio-ekonomiese impak van vloede op die plaaslike inwoners te bepaal ten einde maniere te vind om die gevolge van oorstromings in die landelike gebiede van die Cuvelai teen te werk. Ernstige oorstromings in 2009, 2011 en 2012 het 'n aansienlike impak op die Namibiese ekonomie gehad met geraamde verliese van ongeveer US$136.4 million (NAD1364 million) in direkte skade en US$78.2million (NAD780 million) in indirekte verliese vir die land. Ongeveer een persent (1%) van die land se 2009 bruto binnelandse produk (BBP) is benut om die gevolge van hierdie oorstromings aan te spreek. Landelike inwoners in die Cuvelai-opvangsgebied woon op kleinhoewes, plaaslik bekend as ekove, wat toegeken word deur plaaslike gemeenskapsleierskap. Hulle is hoofsaaklik afhanklik van bestaansboerdery. Aangesien hoër-liggende gebiede met goeie landboupotensiaal toenemend skaarser word, word nuwe kleinhoewes toegeken in laer-liggende gebiede, waar die negatiewe gevolge van oorstromings op inwoners erger kan wees. Skade aan gewasse, landbougrond en weiding, boorde en vee deur oorstromings en soortgelyke rampe is dus kommerwekkend. Die doelstelling van die studie was dus om die impak van oorstromings te bepaal, die geografiese of fisiese omstandighede wat plaaslike inwoners in gevaar stel te evalueer, en sosio–ekonomiese toestande wat lei tot kwesbaarheid te bepaal. Verdere doelwitte was om vas te stel of gemeenskapleiers en plaaslike inwoners vloedrisikokaarte kan gebruik om vloedkwesbaarheid te bepaal, in oorleg met plaaslike owerhede en inwoners alternatiewe praktiese aangepaste strategieë vir oorstromings vas te stel en aanbevelings aan die nasionale rampsbestuursbeleid en praktyk waar toepaslik te maak. Tydens die afgelope oorstromings was regeringsinisiatiewe om oorstromings te hanteer korttermyn vloedverligting, grootliks afhanlik van skenker. Om vloede en landbou-klimaatsveranderinge the hanteer, het landelike inwoners nuwe praktyke ontwikkel, sommige van tradisionele aard, om die impak van oorstomings op hulle lewensbestaan the verminder. Ongelukkig word sodanige kennis nie ten volle erken deur beleid, besluitnemers en ramprisikobestuurders nie. As gevolg van hierdie kennisgaping, dien die studiedoelwit om hierdie praktyke saam te stel die doel om gelokaliseerde tradisionele maatreëls aangaande vloedreaksie, versagting en aapasbaarheid te dokumenteer. Verder sal die studie onlangse maatreëls voorstel soos aanbeveel deur die plaaslike landelike inwoners. Ten einde kwalitatiewe data van die gemeenskappe wat in die Cuvelai woon te bekom is daar vir vier maande (Augustus tot November 2012) opnames gedoen by 314 huishoudings, gekies op aanbeveling van die plaaslike owerhede wat insluit 273 vloedslagoffers, 42 gemeenskapsleiers, en 35 huishoudings wat nie deur vloede beïnvloed is nie, vanuit 45 verskillende gemeenskappe. Die kwalitatiewe data is opgeneem, vooraf-gekodeer, verwerk en ontleed in Microsoft Excel, SPSS en STATISTICA om beskrywende en inferensiële statistieke te bekom. Die studie het bevind dat daar 'n behoefte is om die vlak van gemeenskapsdeelname te bevorder, inkoop en betrokkenheid by die ramp risikobestuurstrategieë te verkry ten einde die tegniese gaping tussen vroeë waarskuwingsmeganismes en inheemse kennis te verminder. Die studie het ook getoon dat huishoudings met ‘n gekombineerde sosio-ekonomiese en geografiese kwesbaarheid groter newe-effekte ondervind van vloedrampe. Die twee kwesbaarhede is egter nie direk eweredig aanmekaar nie. Ander kwesbare groepe in die samelewing is uitgewys, en strukturele en nie-strukturele versagting en paraatheidsmaatreëls op huishoudelike vlak is deur die inwoners aanbeveel. Die studie se doelwit is om die aanpasbaarheid van die plaaslike inwoners tydens oorstromings te bevorder, en sodoende die impak te verminder. Dokumentasie van hierdie tegniese en inheemse kennis sal dien as 'n kennisbasis wat saamgestel en geïntegreer kan word in 'n effektiewe gemeenskapsvriendelike vroeë vloedwaarskuwingstelsel. Indien hierdie inisiatief ondersteuning vind op beleidsvlak, kan dit bydra tot die prioritisering van vloed- en rampreaksie in ontwikkelingbeplanning en uitvoering.

Following the construction of the Pongolapoort Dam in 1974, the potential impacts on the lower Phongolo River and floodplain due to alterations in the natural flow regime have caused concerns. Fish communities and population structures are directly influenced by these alterations. The only protected section of the Phongolo River is a 15 km reach and its associated pans that flow through the Ndumo Game Reserve. Historic data shows that the community and population structure of the fish in the Phongolo Floodplain has changed as a result of irregular flood releases. The Ndumo Game Reserve plays an important role in the conservation of many ecologically and economically important species as the pans inside the reserve serve as a refuge area in which these species can breed to replenish the fish numbers in the Phongolo River. The fish diversity inside the Ndumo Game Reserve is also higher when compared to outside. During the high flow period fish move into the floodplain pans as a result of the higher water level. Oreochromis mossambicus, the most common species found in this area, utilize Nyamiti Pan for breeding but the health of this species is under pressure due to severe infestations of Lernaea cyprinacaea and nematode parasites. Lernaea cyprinacaea is a parasitic copepod associated with the introduced exotic fish species Cyprinus carpio which is found in large numbers in various pans inside Ndumo Game Reserve. The presence of this alien species in the refuge area raises concerns as it competes for the same resources as the economically important native fish species. Nyamiti Pan is largely populated by adult cichlid species between the ages of six and ten years old. The importance of flood releases which simulate natural flow regime is emphasised by the negative impacts irregular floods have on fish health, community and population structure. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Following the construction of the Pongolapoort Dam in 1974, the potential impacts on the lower Phongolo River and floodplain due to alterations in the natural flow regime have caused concerns. Fish communities and population structures are directly influenced by these alterations. The only protected section of the Phongolo River is a 15 km reach and its associated pans that flow through the Ndumo Game Reserve. Historic data shows that the community and population structure of the fish in the Phongolo Floodplain has changed as a result of irregular flood releases. The Ndumo Game Reserve plays an important role in the conservation of many ecologically and economically important species as the pans inside the reserve serve as a refuge area in which these species can breed to replenish the fish numbers in the Phongolo River. The fish diversity inside the Ndumo Game Reserve is also higher when compared to outside. During the high flow period fish move into the floodplain pans as a result of the higher water level. Oreochromis mossambicus, the most common species found in this area, utilize Nyamiti Pan for breeding but the health of this species is under pressure due to severe infestations of Lernaea cyprinacaea and nematode parasites. Lernaea cyprinacaea is a parasitic copepod associated with the introduced exotic fish species Cyprinus carpio which is found in large numbers in various pans inside Ndumo Game Reserve. The presence of this alien species in the refuge area raises concerns as it competes for the same resources as the economically important native fish species. Nyamiti Pan is largely populated by adult cichlid species between the ages of six and ten years old. The importance of flood releases which simulate natural flow regime is emphasised by the negative impacts irregular floods have on fish health, community and population structure. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: The Francou and Rodier (1967) empirical approach uses the original concept of envelope curves for the definition of the regional maximum flood (RMF). Kovacs (1980) adopted the Francou and Rodier empirical flood calculation method and applied it to 355 catchments in South Africa. He revised his study in 1988 to also include the southern portions of the Southern Africa subcontinent. No method other than the Francou and Rodier empirical flood approach in the reviewed literature was found to be suitable for the purpose of this study. Therefore the Francou and Rodier empirical approach, as applied by Kovacs in 1988, was reapplied and used in this study to update the RMF for Lesotho. Maximum recorded flood peaks were derived from annual maximum time series and an up to date catalogue of flood peaks for 29 catchments was compiled for Lesotho. The maximum recorded flood peaks were then plotted on the logarithmic scale against their corresponding catchment areas. There are 3 major river systems that divide Lesotho into hydrologically homogenous basins. Envelope curves were drawn on the upper bound of the cloud of plotted points for these 3 river basins. These envelope curves represent the maximum flood peaks that can reasonably be expected to occur within the respective river basins in Lesotho. / AFRIKAANSE OPSOMMING: Francou en Rodier (1967) se empiriese benadering maak gebruik van die oorspronklike konsep van boonste limiet kurwes vir die definisie van die streeks maksimum vloed (SMV). Kovacs (1980) het die Francou en Rodier empiriese vloed berekening metode toegepas op 355 opvanggebiede in Suid-Afrika. Hy hersien sy studie in 1988 om ook die suidelike gedeeltes van die Suider-Afrikaanse subkontinent in te sluit. Geen ander metode as die Francou en Rodier empiriese vloed benadering is in die literatuur gevind wat as geskik aanvaar kan word vir die doel van hierdie studie nie. Daarom is die Francou en Rodier empiriese benadering, soos toegepas deur Kovacs in 1988, weer in hierdie studie toegepas en gebruik om die SMV metode vir Lesotho op te dateer. Maksimum aangetekende vloedpieke is verkry vanuit jaarlikse maksimum tyd-reekse en ʼn opgedateerde katalogus van vloedpieke vir 29 opvanggebiede saamgestel vir Lesotho. Die maksimum aangetekende vloedpieke is grafies aangetoon op logaritmiese skaal teenoor hul opvanggebiede. Daar is 3 groot rivierstelsels wat Lesotho in hidrologiese homogene gebiede verdeel. Boonste limiet kurwes is opgestel om die boonste grens van die gestipte punte vir hierdie 3 gebiede aan te toon. Hierdie krommes verteenwoordig die maksimum vloedpieke wat redelikerwys verwag kan word om binne die onderskeie rivierstelsels in Lesotho voor te kan kom.

As easy target reservoirs are depleted around the world, the need for intelligent enhanced oil recovery (EOR) methods increases. The first part of this work is focused on modeling aspects of novel chemical EOR methods for naturally fractured reservoirs (NFR) involving wettability modification towards more water wet conditions. The wettability of preferentially oil wet carbonates can be modified to more water wet conditions using alkali and/or surfactant solutions. This helps the oil production by increasing the rate of spontaneous imbibition of water from fractures into the matrix. This novel method cannot be successfully implemented in the field unless all of the mechanisms involved in this process are fully understood. A wettability alteration model is developed and implemented in the chemical flooding simulator, UTCHEM. A combination of laboratory experimental results and modeling is then used to understand the mechanisms involved in this process and their relative importance. The second part of this work is focused on modeling surfactant/polymer floods using a fully implicit scheme. A fully implicit chemical flooding module with comprehensive oil/brine/surfactant phase behavior is developed and implemented in general purpose adaptive simulator, GPAS. GPAS is a fully implicit, parallel EOS compositional reservoir simulator developed at The University of Texas at Austin. The developed chemical flooding module is then validated against UTCHEM. / text

No description available.

Deux volets distincts de l'hydrologie sont abordés, prévision et prédétermination, au travers d'une problématique commune : le transfert à l'exutoire des bassins versants d' une information hydrologique distribuée. Dans le domaine de la prévision des crues, la technologie radar procure une information pluviométrique spatialement continue. Les hydrologues disposent ainsi en temps réel de la connaissance des champs de pluie, atout indéniable pour l'anticipation des crues notamment sur des petits bassins versants par le biais de la modélisation de la pluie en débit. Dans le cadre de la méthode AIGA d'alerte crues, développée au Cemagref, une modélisation mise en oeuvre à l'échelle du pixel de pluie fournit une cartographie des contributions de débit des pixels. Dans le domaine de la prédétermination, le Cemagref a développé la méthode SHYREG qui associe un modèle régionalisé de simulation de pluies horaires à une modélisation de la pluie en débit. Une estimation statistique régionale des pluies et des débits spécifiques de différentes durées, dans une large plage de fréquence (du courant à l'exceptionnel) peut ainsi être proposée et cartographiée. L'objectif du travail présenté est d'étudier et d'élaborer des méthodologies simples de transfert de ces deux informations débitmétriques discrétisées information temps réel pour le volet prévision et information statistique pour le volet prédétermination - à l'information débit à l'exutoire du bassin versant. La méthodologie met en oeuvre des informations spatiales et une modélisation de la pluie en débit. Pour répondre à l'objectif fixé, trois axes de travail sont développés. Le premier est l'étude du comportement d'un modèle pluie-débit simple développé pour être mis en oeuvre à la maille du km². On examine en particulier s'il satisfait les caractéristiques d'invariance et de parcimonie souhaitée pour une utilisation à la fois en reconstitution de crues et en simulation. Le second axe de travail concerne l'agglomération, en prédétermination, de l'information débit statistique connue au km² pour l'estimation des quantiles de débit à l' exutoire de bassins versants de superficie plus importante dans le cadre de la méthode SHYREG. Il s'agit de tenir compte de deux phénomènes hydrologiques distincts : l'abattement spatial de la pluie et le transfert dans le réseau hydraulique. Le troisième axe de travail concerne l'agglomération de l'information hydrologique distribuée pour la reconstitution des crues dans le cadre de l'outil AIGA d'alerte crues. Différentes modélisations sont proposées pour transférer à l'exutoire les contributions des débits modélisées aux pixels. / We address the routing of distributed hydrological information to the outlet of watersheds, in the fields of flood forecasting and flood prediction on ungauged watersheds in the French Mediterranean area.Flood forecasting can benefit of areal rainfall data provided in real-time by radar networks. This data used as an input to rainfall runoff models gives access to flood anticipation on small ungauged watersheds. Within the framework of the AIGA method, developed by CEMAGREF to provide floods alert, a rainfall-runoff model is implemented at the spatial resolution of the radar data, thus providing a map of the 1 km² pixel contributions to the runoff at the catchment outlet.Flood prediction consists of assessing the frequency of occurrence of floods of different given magnitude without reference to the times at which they would occur. The SHYREG flood prediction method, developed by Cemagref associates a regionalized rainfall model with a rainfall-runoff model. It provides grids of statistical estimates of rain and runoff for various duration and return periods. Our purpose is to study and work out simple methodologies to aggregate these two gridded hydrological data - real time information for the AIGA forecasting method and statistical data for the SHYREG prediction method to the catchments outlets. Our methodology implements distributed information and a rainfall-runoff model. We have first studied the behaviour of a simple rainfall-runoff model developed to be implemented in a gridded resolution (1 km² cells) for prediction as well as for forecasting purposes. We have checked that the model parameters show no redundancy and no link with the characteristics of the rainfall events. We have then addressed the question of the aggregation of gridded hydrological data. Within the SHYREG method, it consists of assessing statistical flow estimates at catchments outlets, knowing simulated flow distributions in each cell of the catchments. This aggregation would combine two distinct hydrological phenomena: areal reduction of rainfall and discharge attenuation in the channel network. Within the AIGA method, we have focused on the routing function of the rainfall-runoff model at the 1 km² cell scale, this scale being the first step of the runoff routing from the production area to the outlet of the catchment. We have then produced streamflow hindcasts for selected observed events using different routing function, within our rainfall-runoff model.

D’un point de vue climatique la région méditerranéenne est propice aux évènements pluvio-orageux intenses, particulièrement en automne. Ces pluies s’abattent sur des bassins versants escarpés. La promptitude des crues ne laisse qu’un temps très court pour la prévision. L’amplitude de ces crues dépend de la grande variabilité des pluies et des caractéristiques des bassins versants. Les réseaux d'observations ne sont habituellement pas adaptés à ces petites échelles spatiales et l'intensité des événements affecte souvent la fiabilité des données quand elles existent d’où l’existence de bassin non jaugés. La régionalisation en hydrologie s’attache à la détermination de variables hydrologiques aux endroits où ces données manquent. L’objectif de cette thèse est de contribuer à poser les bases d’une méthodologie adaptée à la transposition des paramètres d'un modèle hydrologique distribué dédié aux crues rapides de bassins versants bien instrumentés à des bassins versants non jaugés, et ce sur une large zone d’étude. L’outil utilisé est le modèle hydrologique distribué MARINE [Roux et al., 2011] dont l’une des originalités est de disposer d’un modèle adjoint permettant de mener à bien des calibrations et des analyses de sensibilité spatio-temporelles qui servent à améliorer la compréhension des mécanismes de crue et à l’assimilation de données en temps réel pour la prévision. L’étude des sensibilités du modèle MARINE aborde la compréhension des processus physiques. Une large gamme de comportements hydrologiques est explorée. On met en avant quelques types de comportements des bassins versants pour la région d’étude [Garambois et al., 2012a]. Une sélection des évènements de calibration et une technique de calibration multi évènements aident à l’extraction d’un jeu de paramètres par bassin versant. Ces paramétrisations sont testées sur des évènements de validation. Une méthode de décomposition de la variance des résultats conduit aux sensibilités temporelles du modèle à ses paramètres. Cela permet de mieux appréhender la dynamique des processus physiques rapides en jeu lors de ces crues [Garambois et al., 2012c]. Les paramétrisations retenues sont transférées à l’aide de similarités hydrologiques sur des bassins versants non jaugés, à des fins de prévision opérationnelle / Climate and orography in the Mediterranean region tend to promote intense rainfalls, particularly in autumn. Storms often hit steep catchments. Flood quickness only let a very short time lapse for forecasts. Peak flow intensity depends on the great variability of rainfalls and catchment characteristics. As a matter of facts, observation networks are not adapted to these small space-time scales and event severity often affects data fiability when they exist thus the notion of ungauged catchment emerges. Regionalization in hydrology seeks to determine hydrological variables at locations where these data lack. This work contributes to pose the bases of a methodology adapted to transpose parameterizations of a flash flood dedicated distributed hydrologic model from gauged catchments to ungauged ones, and for a large study area. The MARINE distributed hydrologic model is used [Roux et al., 2011], its originality lies in the automatically differentiated adjoint model able to perform calibrations and spatial-temporal sensitivity analysis, in order to improve understanding in flash flood generating mechanisms and real time data assimilation for hydrometeorological forecasts. MARINE sensitivity analysis addresses the question of physical process understanding. A large panel of hydrologic behaviours is explored. General catchment behaviours are highlighted for the study area [Garambois et al., 2012a]. Selected flood events and a multiple events calibration technique help to extract catchment parameter sets. Those parameterizations are tested on validation events. A variance decomposition method leads to parameter temporal sensitivity analysis. It enables better understanding in catching dynamics of physical processes involved in flash floods formation [Garambois et al., 2012c]. Parameterizations are then transfered from gauged catchments with hydrologic similarity to ungauged ones with a view to develop real time flood forecasting

This paper analyzes the anatomical response of Pinus pinaster Ait. following wounding by flash floods. A total of 14 wood samples were taken from 14 different scarred trees located on the river banks of the Arroyo Cabrera torrent (Spanish Central System). In addition, 20 increment cores were collected from undisturbed and healthy P. pinaster trees to build a local reference chronology. For the injured trees, analysis focused on growth changes in early earlywood (EE) tracheids, namely on differences in (i) lumen size; (ii) cell-wall percentage and cell-wall thickness; (iii) radial length and tangential width of tracheids; as well as (iv) in the abundance of resin ducts in earlywood (EW) and latewood (LW) following wounding. Results indicate that tissues bordering flash-flood wounds are characterized by reduced growth rates and a decrease of EE tracheid lumen area by 51%. In addition, cell-wall percentage increases by 34% in the increment rings formed after the event and significant changes are observed in the radial length and tangential width of EE tracheids. Observations on resin ducts do not yield any significant results. Based on these anatomical parameters, detecting and dating past flash-flood events in growth rings is now possible for Mediterranean species, specifically P. pinaster.

The object of this dissertation is to describe the influence of water works on the outflow from a watershed through the Hydrologic Modelling System Hec HMS. It is a direct application to the particular watershed of the Bílský Stream. In the theoretical part about relevant literature, solutions to the topics related to this issue are found. It focuses especially on the water balance in the watershed; the outflow from the watershed and other factors by which the watershed is influenced; extreme flows and flood activity with appropriate security steps such as water basins. At the end of the part on the literature, there are five different systems for creating hydrologic models with the specialisation on the Hec HMS model. The practical part is about preparing input data for the hydrologic model and its subsequent creation. Particular runoff from different N-year precipitation (N = 2, 10, 50 and 100) are compared. Two hydrologic models have been created for comparison, one with the watershed without a reservoir and the second one with a reservoir included. The resultant part is about watching flows, volumes of runoffs and the tranformation of the flood wave in a reservoir between N-year precipitation and two different models of watershed.