Reservoirs and dams are often situated in the mountains upstream of cities and towns. This implies a theoretical but difficult to evaluate hazard potential for downstream communities. This paper reflects experiences of the related safety analysis practice including the steps from the breach estimation towards the drawing of special hazard maps.

It is essential to understand the mechanics of ice load and how it affects concrete dams located in a cold climate, such as Sweden, where the temperature becomes sufficiently cold to freeze the surface of the reservoir. The purpose of this thesis is to study ice load distribution along concrete dams, and its response during the application of an ice load. Two types of concrete dams were analysed, an arch dam and a buttress dam. For these dams, the influence from different parameters on the ice load distribution along the dams is studied. In addition to this, a study on how the ice load affects dam stability had also been performed. Stability analyses based on the finite element method were performed using both linear and nonlinear formulation of the interaction behaviour between the base of the dam and the underlying rock. A parametric study of ice sheet expansion on different dam types and geometries were performed. The expansion of the ice sheet was assumed to either be caused by a constant temperature 15 ˚C uniformly distributed over the ice thickness, or by a temperature gradient from 15 ˚C at the top surface of the ice sheet and 0 ˚C at the bottom. The parametric study also includes an investigation about influence of the shape of the reservoir beaches, where it either had a perpendicular shape towards the surface of the dam, or it had an angle of 30˚ with the dam surface. In the linear stability analysis, the structure continued to deform with increasing of the resultant pressure until it reached nonlinearity. The dam deflection had a linear relation with the applied ice load force until it reached the point when structure behaviour was nonlinear. The structure failed due to sliding, overturning or combination of both sliding and overturning. A material failure can also occur if the nonlinear material behaviour is considered, however this was not considered in this study. The parametric study showed that the ice load distribution was less near the beaches, and the distribution of the load on the concrete dam was higher near the top surface of the ice sheet. It was also shown in the study that the distribution of the ice load along the dam was as a cosine function where it had the maximum value at the buttress and the minimum at monolith connections. The result also showed that the load distribution over the thickness of the ice sheet was the same along the dam, regardless of the shape of the beaches or the length of the ice sheet. / Det är viktigt att förstå hur islasten beter sig och hur den påverkar betongdammar som är belägna i kallt klimat, som t.ex. Sverige, där temperaturen blir tillräckligt låg för att frysa ytvattnet i en flod. Syftet med detta examensarbete är att studera isbelastningsfördelningen längs en betongdamm och dess respons under en belastningen. Två olika typer av betongdammar har analyserats, vilka är valvdamm samt lamelldamm. För dessa, studerades det hur olika parametrar påverkar lastfördelningen från istrycket längsmed dessa dammar. Slutligen har det studerats hur islasten påverkar dammsäkerheten och risken för dammbrott. Inverkan från interaktionen mellan dammen och det underliggande berget som linjär eller olinjärt har studerats i stabilitetsanalyser baserade på finita elementmetoden. En parameterstudie har också genomförts för olika dammtyper och geometrier där islasten orsakades av en expansion av isytan. Denna expansion antogs vara orsakad av antingen av en jämn fördelad temperatur över istjockleken på 15 ˚C, eller en temperaturgradient över istjockleken med +15 ˚C på den övre ytan och 0 °C vid isens bottenyta. Den parametriska studien beaktar även inverkan från utformningen av stränderna, där den har definierats som antingen vinkelrät mot dammen eller med en lutande vinkel på 30 grader. I fallet med linjära stabilitetsanalyser kommer konstruktionen att fortsätta att deformeras som ett resultat av ökande resulterande tryckkraft. Dammens deformation har ett linjärt förhållande med den applicerade islasten till dess att den når en punkt då strukturens beteende övergå till olinjärt. Strukturens brottmod kan uppstå på grund av glidning, stjälpning eller i en kombination av både glidning och stjälpning. materialbrott kan uppstå om icke-lineariteterna beaktas. Dammen gick till brott på grund av glidning, vältning eller i kombinationen av dessa då. Materialbrott kan uppstå om icke-linjära materialmodeller inkluderas, men detta beaktades dock ej i denna studie. Den parametriska studien visar att isbelastningen är mindre nära stränderna och att belastningen på betongdammen är högre vid isens ovanyta. Studien visar att islastfördelningen längsmed dammen liknar en cosinusfunktion som når sitt maximum vid stödskivan och sitt minimum vid monolitanslutningen. Resultatet visar även att islastfördelningen genom islastens tjocklek har samma form längsmed dammen oavsett utformningen av stränder eller istäckets längd.

No description available.

Throughout the years, dams have had important function for humans. However, many dams have today lost their function, which raises the question of dam removal. The outcomes of dam removal and their effects on fish communities are not fully investigated, which emphasizes the importance of continuing to study the effect of removal. In this study, I investigated whether or not dam removal in small lake outlets affected fish diversity. I also investigated the effects of the lake area and concentration of nutrients. The data collection was carried out in parts of Värmland, Dalarna and Västmanland counties, where 27 lakes, both with and without removed dams, were sampled. To sample fish, four to eight multimesh gill nets (depending on the area of the lake) were placed at varying depths. Water samples to measure nutrient concentrations were collected in places where the lakes were the deepest. A total of 3 223 individuals and 11 species were caught, with the most common species being perch. The effective species number varied between 1 and 3.44. There was a positive relationship between lake area and fish diversity. Dam removal, concentration of total phosphorus and total nitrogen had no effect on fish diversity. Dam removals can be considered as disturbances in complex systems and their effects may vary. Fish diversity is affected by colonization period and interactions between species, which likely takes long, which may explain why area but not dam removal affected fish diversity in my study. The lakes in the study were relatively homogeneous with respect to nutrient availability, which likely explains why nutrient concentration did not affect fish diversity. It is important to continue investigating the consequences of dam removal in other habitats than rivers, so that management of different water habitats can be carried out in the best way. / Dammar har genom tiderna fyllt en viktig funktion för människan. Många dammar har dock idag tappat sin funktion, vilket lyfter frågan om dammutrivning. Utfallen av dammutrivningar och dess effekter på fisksamhället är inte helt utredda, vilket trycker på vikten att fortsätta att studera effekten av utrivningar. I den här studien undersökte jag om dammutrivningar i mindre sjöutlopp påverkade fiskdiversiteten. Jag undersökte även effekterna av sjöarnas area och koncentration av näringsämnen. Datainsamlingen genomfördes i delar av Värmlands, Dalarnas och Västmanlands län, där 27 sjöar, både med och utan utriven damm, provtogs. För att provta fisk användes fyra till åtta provfiskenät (beroende på sjöns area) som placerades i varierande djup. Vattenproverna samlades in på platser där sjöarna var som allra djupast. Totalt fångades 3223 individer och 11 arter där den vanligaste arten var abborre. Det effektiva artantalet varierade mellan 1 och 3,44. Det fanns ett positivt samband mellan sjöarea och fiskdiversitet. Dammutrivning eller koncentration av total-fosfor eller total-kväve visade sig inte ha någon effekt på fiskdiversiteten. Dammutrivningar kan ses som störningar i komplexa system och att effekterna av dem varierar. Fiskdiversitet påverkas av koloniseringsperiod och interaktioner mellan arter, vilket sannolikt tar lång tid, något som kan förklara varför area men inte dammutrivningar inte påverkade fiskarnas diversitet i min studie. Sjöarna i studien var relativt homogena med avseende på näringstillgång, vilket sannolikt förklarar varför näringsämneskoncentrationen inte påverkade fiskdiversiteten. Det är viktigt att fortsätta arbeta med konsekvenserna av dammutrivningar i andra miljöer utöver älvar så att förvaltning av olika vattenmiljöer kan göras på bästa sätt.

Eutrophication is a nutrient enrichment of dams and lakes. Increased eutrophication in dams results in blooms of cyanobacteria. Cyanobacteria are troublesome as they form massive surface scums, impart taste and odour to the water. Some strains of cyanobacteria such as Microcystis aeruginosa are dangerous to humans and animals. They produce toxins that can kill animals drinking the contaminated water and have also been implicated in human illnesses. The study investigated the effectiveness of techniques deployed in controlling cyanobacterial growth in Rietvlei, Roodeplaat and Hartbeespoort Dams. This was done by interpreting data from April 2010 to March 2012. The conditions in the three dams show that Microcystis produced toxins in the summer season and all the variables analysed were favourable for the production of toxins. The methods deployed to rehabilitate the dams do not completely solve the problems of toxins experienced by the dams. / Environmental Sciences / M. Sc. (Environmental Management)

The vegetation of the Nooitgedacht section of the Loskop Dam Nature Reserve resembles Bankenveld vegetation and differs from the other areas of the reserve. This study was undertaken to identify, classify, and describe the plant communities present on this section, and to determine their veld condition. The Braun-Blanquet approach was followed to classify the different plant communities. A total number of 170 sample plots (100m2) were placed in all homogeneous vegetation units in a randomly stratified basis. The Ecological Index Method (EIM) was used to determine the veld condition. Data were collected using the steppoint method and incorporated into the GRAZE model from where the veld condition was calculated. A minimum of 400 step points were surveyed in each community with more points in the larger communities. Plant community data was analysed using the JUICE software program. A total of 11 plant communities were identified. The overall veld condition score indicates the vegetation to be in a good condition, resulting in a high grazing capacity. / Environmental Sciences / M. Sc. (Nature Conservation)

Eutrophication is a nutrient enrichment of dams and lakes. Increased eutrophication in dams results in blooms of cyanobacteria. Cyanobacteria are troublesome as they form massive surface scums, impart taste and odour to the water. Some strains of cyanobacteria such as Microcystis aeruginosa are dangerous to humans and animals. They produce toxins that can kill animals drinking the contaminated water and have also been implicated in human illnesses. The study investigated the effectiveness of techniques deployed in controlling cyanobacterial growth in Rietvlei, Roodeplaat and Hartbeespoort Dams. This was done by interpreting data from April 2010 to March 2012. The conditions in the three dams show that Microcystis produced toxins in the summer season and all the variables analysed were favourable for the production of toxins. The methods deployed to rehabilitate the dams do not completely solve the problems of toxins experienced by the dams. / Environmental Sciences / M. Sc. (Environmental Management)

The vegetation of the Nooitgedacht section of the Loskop Dam Nature Reserve resembles Bankenveld vegetation and differs from the other areas of the reserve. This study was undertaken to identify, classify, and describe the plant communities present on this section, and to determine their veld condition. The Braun-Blanquet approach was followed to classify the different plant communities. A total number of 170 sample plots (100m2) were placed in all homogeneous vegetation units in a randomly stratified basis. The Ecological Index Method (EIM) was used to determine the veld condition. Data were collected using the steppoint method and incorporated into the GRAZE model from where the veld condition was calculated. A minimum of 400 step points were surveyed in each community with more points in the larger communities. Plant community data was analysed using the JUICE software program. A total of 11 plant communities were identified. The overall veld condition score indicates the vegetation to be in a good condition, resulting in a high grazing capacity. / Environmental Sciences / M. Sc. (Nature Conservation)

This study assesses the contribution of agricultural non-point source pollution, to poor water quality of the Vaal River within the Grootdraai dam catchment area. The study evaluates agricultural pollutants affecting the quality of water within the study area. The impact of agricultural non-point source pollution on the water quality of the Vaal River was evaluated by establishing a correlation between the quantity of polluted runoff reaching the River and the quantity of measured nitrates and phosphates in its waters. A questionnaire using random sampling was used to capture data from 15 commercial farmers 35 local residents and the Department of Water Affairs management. The results of the study show that agricultural nutrients are heavily impacting and compromising the water quality of the Grootdraai Dam. The mean concentrations of Nitrogen and Phosphorus were found to be well above the water quality guidelines there by promoting eutrophication. / Environmental Sciences / M. Sc. (Environmental Management)

Emerging river policy has launched small dam removal as a viable option to meet the ecological and social demands for river restoration. As small dam removals gain precedence as a policy tool in river restoration projects there exists a glaring gap in the social considerations, in particular how small dam removals may affect existing community conditions. In order to determine the community impacts that may result, a case study of the Brownsville Dam Removal, in Brownsville Oregon was investigated to address two questions: 1) how has the Brownsville Dam removal affected the social and economic conditions of the community and 2) what indicators can be used to characterize and monitor the impacts. Twenty-nine semi-structured interviews were conducted with four community affiliations: 1) Canal Company members; 2) Calapooia Watershed Council members; 3) City Officials; and 4) community residents. A participatory social impact assessment (SIA) approach was used to validate existing and/or emergent impacts and indicators. The semi-structured interviews assisted in the development of a matrix of impacts and indicators specific to small dam removal. The local impacts and indicators were operationalized and measured. Findings suggest that the social and economic impacts when distributed across the community are minimal in this case of small dam removal. Because local data availability is limited, it was determined that the traditional social impact assessment framework can be vastly improved through the engagement of the community. This research further suggests that when collaboration is extended beyond a unidirectional flow of information (which is often the case in a traditional SIA), issues and concerns are open to deliberation in a non-threatening arena. The Calapooia Watershed Council served as the forum through which the residents of Brownsville were able to enhance their participation in decision making. This also contributed to a learning process that in the end furthered the community's understanding of the dynamic physical changes to the Calapooia River as well as their capacity to solve complex decisions. The case also demonstrated that collective learning is a reflective process of adjustment to the changing circumstances in which the community came to perceive, interpret, and act upon their interest. With a growing number of collaborative partnerships of watershed based management, distinguishable by their decentralized, participatory engagement of stakeholders, it may be likely that these place-based mechanisms will become the nexus to the successful coordination of small dam removal deliberation in the future. / Graduation date: 2010