Human land use practices such as urbanization and agriculture contribute excess nutrients (nitrogen and phosphorus) and runoff volumes to rivers that degrade aquatic ecosystems and cause a loss of river functions such as nutrient processing and flood attenuation. Floodplain restoration increases floodplain exchange and is commonly implemented to improve water quality and reduce flood impacts at watershed scales. However, the effect of multiple restoration projects at the watershed scale is not well studied. We addressed this knowledge gap by two studies. The first study evaluated the impact of cumulative and spatially varying Stage-0 and bankfull floodplain restoration on nitrate removal in a generic 4th-order Virginia Piedmont watershed for small and sub-annual storm sizes (i.e. 2-year, 1-year, half-year, and monthly recurrence intervals). We used HEC-RAS hydraulics results from a prior study together with a nitrate removal model coded in R. Results indicated that watershed nitrate removal varied depending on the location of restoration in the watershed and where removal was evaluated. The greatest reductions in nitrate loads were observed in the same part of the river network where restoration occurred, with diminished impacts downstream. Removal also increased with increasing stream order/river size. However, removal was generally of small magnitude, with up to 1% or 19% of the watershed load removed for median or 90th-percentile removal rates, respectively. We estimated removal for our restoration scenarios under the Chesapeake Bay Program Protocols and found the removal rate to also be a critical factor in determining the efficiency of restoration project. Other controlling factors for nitrate removal were the amount of restoration and storm size. The second study entailed modeling cumulative restoration in a case study watershed to assess the impacts on nutrient removal and flood attenuation. We built a 1D HEC-RAS model of the 4th-order Gwynns Falls watershed near Baltimore MD using georeferenced HEC-RAS model geometries from the Maryland Department of the Environment and simulated unsteady stormflow hydraulics due to cumulative Stage-0 floodplain restoration for small and sub-annual storms. Restoration actually increased peak flow on the main channel (up to 0.9%) due to slowing of the flood wave on the main channel which was then better synchronized with tributary inflows. Restoration increased nitrate removal but at low levels (up to 0.12% or 2.6% removal for a median and 90th-percentile removal rate respectively) due to the small footprint of restoration in the watershed (up to 21.4% of the main channel was restored). These small and sometimes adverse outcomes occurred in response to what would be expensive restoration. Therefore, we argue for large-scale solutions to address watershed-scale water quality and flooding issues yet acknowledge re-evaluation of restoration goals against other societal priorities may be necessary. Overall, our results highlight the potential value and limitations of floodplain restoration in reducing flooding and nitrate exports at the channel network scale and provide practical insight for application of floodplain modeling at the watershed scale. / Master of Science / Human land use practices such as building cities and farms adds nutrients (nitrogen and phosphorus) and increase storm flows in rivers downstream. While nutrients and flows are needed for humans and wildlife, too much of either can harm aquatic organisms and endanger people and property. Floodplain restoration is a common river engineering technique that increases exchange between the river channel and low-lying areas next to rivers known as floodplains. Floodplains are natural features, but people have reduced river flows between channels and floodplains in many ways. For example, by allowing sediments to build up in floodplains or building levees that separate channels from adjacent floodplains. Increasing floodplain exchange by floodplain restoration is commonly implemented to improve water quality and reduce the impact of flooding in watersheds, which are large areas that drain to a single river. However, while the goals of restoration are often at watershed scales, the effect of multiple restoration projects at that watershed scale is not well studied. We addressed this knowledge gap by two studies. The first study evaluated the impact of multiple restoration projects and project locations in a generic (average/typical) watershed on nitrate removal. We used a nitrate removal model and the results from a prior study that modeled the stormflow behavior resulting from floodplain restoration. Results indicated that watershed nitrate removal varied depended on the location of restoration in the watershed and where removal was evaluated. The most nitrate was removed where restoration occurred, with less removal downstream in the watershed. Removal also increased with increasing river size. However, removal was generally small with up to 1% or 19% of the watershed load removed for a smaller and larger nitrate removal rate, respectively. Other factors that changed the amount of nitrate removed were the amount of restoration, nitrate removal rate in the floodplains, and storm size. The second study entailed modeling cumulative restoration in a case study watershed to assess the impacts on nitrate removal and reducing flooding. We modeled stormflow for multiple hypothetical restoration projects in the Gwynns Falls watershed and found that restoration can actually increase peak flow when placed in certain locations. Restoration increased removal but at low levels (up to 0.12% or 2.6% for a smaller and larger removal rate) due to the small amount of restoration simulated. These small and sometimes adverse outcomes occurred in response to what would be expensive restoration projects to construct. Therefore, we argue for large-scale solutions to address watershed-scale water quality and flooding issues yet acknowledge that re-evaluation of restoration goals against other societal priorities may be necessary. Overall, our results highlight the potential value and limitations of using floodplain restoration to reduce flooding and nutrient exports and provide practical insight for using our modeling techniques in managing watershed flows and pollution.

The aim of this study was to evaluate restoration methods used in a revegetation project for the heavily disturbed area around the abandoned underground mine Stekenjokk, located in an alpine area in Västerbotten County, Sweden. The studies were initiated in 2013 by Enetjärn Natur AB on behalf of Boliden Mineral AB and several methods were adopted in the purpose of investigating the feasibility of different restoration methods. Seeding, plantation of adult plants and transplantation of vegetation turfs were performed in combination with addition of organic matter. In addition, ‘safe sites’ were created either by addition of cobbles to the surface, creation of holes in the ground or by putting out coconut mats. All plant material, e.g. seeds, plantation of adult plants and transplantation of vegetation turfs, resulted in new establishment of plants in the area. Spontaneous establishment of plants was also observed in several of the examined plots. Several of the methods used are probably suitable for restoration of the old industrial area in Stekenjokk. However, the success varied among different methods and there was a tendency for higher survival of plants in experimental plots to which soil had been added. A combination of addition of plant material (seeds or adult plants), addition of organic matter and creation of ‘safe sites’ seemed most effective in accelerating revegetation in the heavily degraded area in Stekenjokk. However, sample sizes were small and more studies should be conducted to confirm the generality of this conclusion.

Eutrophication is a global environmental problem, which in Sweden is predominantly in the south of Sweden where there are large agricultural areas. Skellefteå is a small town on the northern coast which has eleven water bodies classified as “poor ecological status” of which Uttersjöträsket is one of them according to the water authorities. Uttersjöträsket has a requirement to achieve good ecological status by 2021. Uttersjöträsket’s agriculture land is from at least 1716 according to historical maps. To be able to restore a eutrophic lake the source of the phosphorus load must be identified.To determine the natural state for Uttersjöträsket the sediment record could be studied. For example, earlier studies have been made in Kassjön in Umeå were they conclude that the beginning of the agriculture area started in the 12th century, which means that Uttersjöträsket could have had agriculture land since before 1716. The municipality of Skellefteå made contact with residents in the area who formed a water group to work towards achieving the goal by 2021. This report will form the basis for the water group to take appropriate measures to reduce the bloom of cyanobacteria and to achieve good ecological status. The conclusions of this report are based on analysis of data and results from previous studies of eutrophic lakes. Many different methods must be done to have a long-lasting impact and to achieve good ecological status in Uttersjöträsket. The focus of the actions should be on the ditch between Yttersjön and Uttersjöträsket as the highest phosphorus load is in that catchment.

No description available.

published_or_final_version / abstract / Conservation / Master / Master of Science in Conservation

published_or_final_version / abstract / Conservation / Master / Master of Science in Conservation

published_or_final_version / Conservation / Master / Master of Science in Conservation

published_or_final_version / abstract / Conservation / Master / Master of Science in Conservation

published_or_final_version / abstract / Conservation / Master / Master of Science in Conservation

published_or_final_version / abstract / Conservation / Master / Master of Science in Conservation