Sökning: "river ice"

Visar resultat 1 - 5 av 24 avhandlingar innehållade orden river ice.

  1. 1. Breaking the ice : effects of ice formation and winter floods on vegetation along streams

    Författare :Lovisa Lind; Christer Nilsson; Christine Weber; Michael Scott; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; anchor ice; climate change; in-stream; riparian; river ice; streams; vegetation;

    Sammanfattning : Streams in cold regions are characterized by unique hydrological processes that control flow regime and water levels. One of the most important processes is the formation, growth and melting of different types of ice in and around the stream channel during winter. LÄS MER

  3. 2. Lateral movements versus stationarity : adaptive alternatives in benthic invertebrates to the seasonal environment in a boreal river

    Författare :Tommy I. Olsson; Umeå universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Benthic invertebrates; cold-hardiness; ice; migrations; overwintering; river; seasonal variations; spatial distribution; spring flood; water level;

    Sammanfattning : Benthic invertebrates inhabiting boreal rivers are exposed to very large seasonal variations in their physical environment. The extremes are in winter when the littoral area freezes solid and in spring when water flow increases rapidly. LÄS MER

  4. 3. Ice, wood and rocks : regulating elements in riverine ecosystems

    Författare :Johanna Engström; Christer Nilsson; Roland Jansson; James Helfield; Tenna Riis; Umeå universitet; []
    Nyckelord :riparian zone; timber floating; river restoration; cut-off side channels; hydrochory; large wood; anchor ice; fish;

    Sammanfattning : Riparian ecosystems are of great importance in the landscape, connecting landscape elements longitudinally and laterally and often encompassing sharp environmental gradients in ecological processes and communities. They are influenced by fluvial disturbances such as flooding, erosion and sediment deposition, which create dynamic and spatially heterogeneous habitats that support a high diversity of species. LÄS MER

  5. 4. A systems approach to ice loads on concrete dams

    Författare :Rikard Hellgren; Richard Malm; Anders Ansell; Erik Nordström; Pierre Legér; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Ice loads; Ice pressure; Dam safety; Concrete dams; Cold regions; Monitoring; Measurements; Concrete Structures; Betongbyggnad;

    Sammanfattning : Dams are mainly used for the storage of water to electricity production and irrigation, or for river regulation. Continuous work to assure a high dam safety level is a prerequisite to minimize the risk for the uncontrolled release of water. LÄS MER

  7. 5. Weichselian glaciations in the middle Notec River region, northwest Poland

    Författare :Gert Pettersson; Kvartärgeologi; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Quaternary Geology; Kvartärgeologi; Geology; Geologi; Vistulian; Weichselian; Lithostratigraphy; Poland; Chodziez; Clast lithology; Clast fabrics; Deglaciation; Ice stream; Sedimentology; Sedimentologi; geomorphology; klimatologi; geomorfologi; climatology;

    Sammanfattning : This thesis presents results of studies on the ice flow pattern and ice movement mechanism during the Weichselian glaciations in the middle Notec River area, NW Poland. A new lithostratigraphy of the study area has been established, based on correlation of stratigraphical position, clast lithology, fabrics and grain size composition of till units. LÄS MER