Kraftindustrin arbetar oavbrutet med att försöka höja och upprätthålla dammsäkerheten i Sverige. Erosionsskydd för fyllningsdammar skall dimensioneras och utformas så att de medverkar till en god dammsäkerhet. Vid dimensionering och projektering av erosionskydd måste vågberäkningar utföras för att bedöma angripande våglast. I Sverige genomförs dessa beräkningar utifrån kraftföretagens riktlinjer för dammsäkerhet, RIDAS. Uträkningarna och bedömningar av våglasterna är ur dammsäkerhetssynpunkt viktiga eftersom de ofta avgör erforderligt fribord.

This master thesis was made to investigate the possibilities of using the Matlab-basedsoftware Basegrain to determine grain size distributions of erosion protections onhydropower dams. Basegrain is a photogrammetric tool developed to generate grainsize distributions and other information about coarse flood sediments by analyzing adigital photo of the stone bed. The investigation was made by validating the ability forBasegrain to assess grain size distributions of various materials smaller than the blocksused in an erosion protection by comparing sieving results or manual measurementswith the results obtained by the program. A statistical comparison was then made bycomparing the results from sieving and the program. The possibilities of using thesame method on existing hydropower dams were then investigated by determiningwhether the method was practically viable or not.The results showed that Basegrain generated grain size distributions for coarse gravelthat were very close to the sieving results.

Today 70 percent of the world's sand beaches are under recession due to erosion. The global warming may have the effect upon the sea level increasing and the erosion increasing on the sand beaches. To save these sand beaches, the erosion must be prevented. Coast erosion shelters like gabions and sea walls are functioning extremely well to protect the land behind the sand beach, but due to the wave reflections, created in front of these so called hard erosion shelters, the erosion of the front beach is accelerated. During the last decades, artificial sand supply (beach nourishment) has been the adopted praxis.

Erosion in coastal areas is a common problem all around the world. The range of the problem depends on several factors, i.e. type of bed-rock and soil, wind and wave climate. Another factor is whether the area is of high interest, i.e. if the area is important for tourism and recreation, if there are houses and other buildings close to the shoreline or if it is a site of special scientific interest.

Hydropower is an important source of energy in Sweden and accounts for about 46 % of the total energy production. Sweden has about 1 200 hydropower plants and with the intention of raising the pressure head of the water and to store water, dams are built by the power plants. The storage reservoirs make it possible to adjust the energy production by demand and season. Dams in connection to the reservoirs are subjected to additional loading during periods of high floods or when an icecap in the winter is formed on the reservoirs. In order to maintain the dam safety, the power companies in Sweden are working with guidelines for dam safety from RIDAS.

This master thesis was made to validate hydropower models of a turbine governor,Kaplan turbine and a Francis turbine in the power system simulator ARISTO atSvenska Kraftnät. The validation was made in three steps. The first step was to makesure the models was implement correctly in the simulator. The second was tocompare the simulation results from the Kaplan turbine model to data from a realhydropower plant. The comparison was made to see how the models could generatesimulation result that was similar to the reference power station.

Research suggests that society's vulnerability to natural disasters along coasts could increase as a result of climate change, which is likely to lead to elevated sea levels and possibly an increase in the occurance of meteorological phenomena such as storms and tropical cyclones. Following the Indian Ocean tsunami disaster in 2004 and Hurricane Katrina in 2005, both of which received considerable media attention, empirical data has indicated that coastal vegetation might be able to protect and reduce damages to coastal communities during tsunami events and tropical cyclones.The aim of the essay has been to study the function of coastal ecosystems as protection against tsunami waves and storms from a risk management perspective, meaning that I have, through an overview of scientific articles, compiled current research on how coastal ecosystems can attenuate storm surges and tsunami waves, and analysed how this knowledge can be put into practice in coastal communities from a risk management perspective, i.e. if coastal ecosystems are a viable risk reduction measure, are practically applicable, and if so, how they could be applied.There is empirical evidence suggesting that coastal ecosystems, particularly mangroves, can reduce the strength of a tsunami wave, but full scientific consensus on this issue has not yet been reached. With regard to protection against storm surges, there is extensive scientific evidence that coastal vegetation can mitigate damages and reduce the height of a storm surge, although the wave has to traverse several kilometres inland through thick vegetation for the protection to be effective. A synthesis in the form of a figure regarding the many physical factors that influence wave development through coastal ecosystems has been created in an attempt to simplify and explain the phenomenon.The conservation and restoration of coastal ecosystems can be justified from a risk management perspective, but planting new forest belts for the purpose of disaster mitigation is quite unrealistic and can rarely be sustainable, since, for protection to be effective, the forest belt must extend several kilometres inland from the coast, and would thus likely prove difficult to implement along coastal societies..

Regulation of rivers by dams and reservoirs is a good example where anthropogenic impact could be considerable both in the local environment, but also has major implications upstream and downstream. This study was accomplished as a literature study of the river Nile, which is extremely important for water supply. The purpose of this study was to investigate the consequences of the construction of the Aswan High Dam, to obtain a consistent flow for water supply, irrigation and power generation in Egypt. Since Egypt has a very hot and dry climate large amounts of water in reservoir is lost to the Nubian aquifer system and by evaporation. The consequences from constructing the dam are considerable.

The aim of this project is to find a concept solution for a wireless transmitting system, installed to transmit data from a hydrophone of the ocean floor down by a wave power generator to the office on shore. The project is a literature review in which previous observations and tests are analyzed and put together to find a solution. The result was a comprehensive solution that includes an acoustic modem to transfer captured information from the bottom to the surface, wirelessly through the water. The information is then sent fron the surface on radio waves through the GSM network to the office on land. Between under and over water there are components to convert information between acoustic waves and radio waves, but also various types of modulation, such as amplitude and frequency modulation is required..

Slopes in fine till soils are exposed to surface erosion due to rainfall, snowmelt and upland water sources. Large areas of road slopes are therefore covered for surface erosion protection. Preventive methods like ditches and trenches are also being used. Silt tills are particularly troublesome since the water can bring the soil into suspension and cause mudslides. Different methods for erosion protection have been studied in this work, with the emphasis placed on rockfill covering. The need for and the dimensioning of this type of covering has been examined in literature and field studies.

During the nineties, ecological handling of urban storm water became very popular in Sweden. Together with Chalmers University of Technology and two Swedish communities, DHI Water and Environment has been doing research of storm water ponds and constructed wetlands. This thesis work is a part of that research project. The work has been applied at the Bäckaslöv storm water treatment plant in Växjö, Sweden. The plant consists of one storm water pond and a downstream constructed wetland.

Severe floods caused by heavy autumn rains in year 2000 raised the question whether measures to reduce the damage from high water levels, in the area surrounding lake Glafsfjorden and along the river Byälven down to lake Vänern, are possible. One option is to reduce flow resistance along the river and thereby lower the maximum water level a given inflow would cause. Good knowledge of hydraulic and hydrological conditions is necessary in order to estimate the effect of such flow-reducing measures. In order to quantify such effect a 1-dimensional hydraulic flow model has been set up for the river Byälven using the software package MIKE 11. The model is more detailed, especially concerning topography and bathymetry, than earlier models used for studies of the river.

In this thesis work a Geographical Information System (GIS) based methodology to identify locations suitable for the installation of wave energy converters has been developed. Parameters of importance have been identified and a GIS-database has been set up, containing data about the marine environment. In a case study of the Swedish west coast the methodology has been applied, resulting in a number of maps showing possible areas. The results show that large areas are suitable for installation of wave energy converters, from a technical and economical point of view. When consideration is taken to other interests in the area, such as navigation, fishing and environmental protection, the size of the suitable area diminishes considerably.

This report describes a thesis project on 15hp. The purpose of the thesis project is to build a laser projector that reacts on sound waves and thus get a laser beam to draw visualizations of sound waves on a wall. The idea was that the design would be independent and not have to be plugged into any audio equipment. This was achieved by absorbing sound waves into a microphone. Another factor was to get a ?do it yourself? -feeling of the design and therefore it was chosen to be constructed using for example, old hard-drives.The result was a relatively large and bulky designed laser projector that can draw sound waves on a wall..

A power system will inevitably be subjected to transient overvoltages, most often produced by switching operations and lightning strikes. These transient overvoltages may harm sensitive equipment without sufficient protection, but it is not an easy task to predict what transients may occur or how they affect the system. A fault occurred in a low voltage system at Forsmark 2012 and overvoltages from lightning were concluded as the probable cause. The three aims with this thesis are to develop and test a model of the power system at Forsmark 3, analyse the transient behaviour of the system when subjected to lightning surges and identify critical parameters, and lastly to provide a tool for investigating the protection of the system. The modelling and simulations were performed in the freely available simulation program LT Spice.