Sediment transport and bathymetric change at Honrafjörður tidal inlet / Sedimenttransport och batymetrisk förändring vid Hornafjörðurs tidvatteninlopp
The relatively calm area behind barrier island are favored locations for harbors even though the navigation through the inlet itself can be challenging. Different measures like dredging or coastal structures might be necessary to ensure the desired water depth to maintain a safe navigation. Iceland as an island country depends strongly on reliable navigational routes connecting harbors to the ocean to ensure its economic wealth. The port of Höfn at the Hornafjörður inlet in southeastern Iceland is the main navigational link for the commercial fishing in this area.The interactions between longshore sediment transport and sediment transport induces by the inlet flow and waves are complex and led to navigational limitations in history. A deeper understanding of local transport patterns is needed to ensure a reliable navigation at the Hornafjörður inlet and limit economic losses in future. Regarding the complexity of the situation around the inlet and the limited data on local hydrodynamics, mathematical modeling must be used to simulate local currents. This article focuses on the research performed and model results gained in connection with the master thesis project “Sediment transport and bathymetric change at Hornafjörður tidal inlet – Field data analysis and mathematical modeling” (Klante, 2018).
Årstidsvariationer i sjöar vid klimatförändringar / Seasonal variations in lakes in northern Sweden in a changing climate
Lakes are suitable sentinels of climate change because they constitute a well defined ecosystem and they respond quickly to changes in climate. Many lakes in the northern hemisphere are covered by ice during winter and they are dimictic, which means that the water circulate two times each year. The ice not only prevents gas exchanges or wind mixing, the ice, together with snow, are also a large obstacles that shortens the growing period for all the producers in the lake by reducing light penetration. Spring bloom of phytoplankton along with onset of stratification might occur earlier in the season if the ice breaks up earlier. Climate warming will lead to higher temperatures and it will alter the mixing conditions as well as affect thermal stratification in lakes. All the lakes included in this study are situated in the southern parts of the region Norrland in Sweden. The average ice break-up between 2001 – 2010 occurs about 12 days earlier compared to the average ice break-up for the period 1916 – 1925 and 11 days earlier compared to 1976 – 1985. The mean annual air temperature in Junsele shows a trend in which the air temperature is getting warmer with time. Higher air temperature shows a correlation with changes in ice phenology, where the lakes experience a shortened ice cover duration.
Smittspridning från avloppsreningsverk – QMRA som beslutsstöd vid ombyggnation av Arvidstorps reningsverk / Pathogen dispersion from wastewater treatment plants – QMRA as decision support in the renovation of Arvidstorp treatment plant
Source water contamination is a main cause of waterborne disease outbreaks in Sweden and municipal sewage discharges often end up in water sources. At Arvidstorp wastewater treatment plant in Trollhättan, a disc filter has been installed with the primary aim of improving phosphorus reduction. To give permission, the County Administrative Board of Västra Götaland called for an investigation into the plant’s microbial load to the Göta River and its health consequences for drinking water consumers. With a pore size of 10 μm in the disc filters, there should be no high expectations of microbial removal. Mechanical separation would require the micro-organisms to be particulate bound, and by precipitation or polymer additives the microbiological separation of the disc filter can be increased. A QMRA model was set up to analyze pathogen dispersion, where indicator organism data were combined with factors such as disease occurrence, operating conditions at the treatment plant, flows and microbiological inactivation in the river. The model was used to calculate the risk of infection for water consumers with respect to Campylobacter, Salmonella, norovirus, Giardia and Cryptosporidium and how this is affected by the disc filter. The QMRA model, which is based on stochastic modeling, has provided a decision support for operational strategies at the sewage treatment plant and has also met the investigation requirements.
Urban, pluvial flooding severely effects infrastructure, buildings and urban life during and after extreme rainfall. In this study, spatial analyses of flood claims from insurance companies and the water utility company of Malmö, VA Syd, are used to better understand the mechanisms and characteristics of pluvial flooding. The same data sets are used to analyse how blue-green infrastructure impacts flood risk. Can blue-green infrastructure for handling of stormwater in urban green spaces be used as a strategy for resilient flood risk management? It was found that flooding during intense rainfall often is located closely to the main overland flow paths and the main sewers, while flooding during rainfall with longer duration seem to be more randomly distributed. Combined sewers are more affected by flooding than separate sewers. Blue-green infrastructure can reduce urban, pluvial flooding. The large-scale spatial distribution of flooding with respect to urban flow paths and drainage system are discussed in relation to the impact of small-scale surface water detention in e.g. detention basins and concave green spaces. The article is based on the authors doctoral thesis (Sörensen, 2018).