Numerical modelling of flash flood event in steep river using Telemac 2D and Sisyphe

Hydrodynamic

Flash flood simulations in a steep catchment using Telemac2D - hydrodynamic rainfall-runoff model

Hydrodynamic

Dynamics of the Seasonal Snowcover in the Artic

Arctic snow cover is important to life on Earth from the microscale soil microarthropod population, to reindeer at the local scale and even the global scale through its impact on the global climate. There is a consensus that global warming will be enhanced towards the Arctic. This will influence the hydrology and snow cover in these regions, which in turn will provide a feedback to climate. There is still a lack of knowledge regarding the impacts to polar hydrology and snow cover; the gaps are even larger with respect to feedback mechanisms. The objective of this study has been to improve the understanding and description of the dynamic processes of an Arctic snow cover. Here, the Arctic climate is studied from the first snow fall to the end of ablation in a series of nine publications grouped into three topics: "Snow Distribution", "Snowmelt and Energy Balance" and "Measurement Methods". The research is based on measurements and observations of climate, snow properties and snow distribution during the period 1992 to 2000 on the tundra in the vicinity of Ny-Ålesund at 78°55'N, 11°56'E at Svalbard, Norway. Improvement of existing snowmelt models has been achieved by the implementation of energy balance calculations and improved description of the snow cover. Ground Penetrating Radar systems as a tool for snow surveying have been improved and used to measure and describe snow distributions over large areas. A snow drift model (SnowTran-3D) has been successfully tested for different scales and topography and was improved to better handle settling of the snow cover due to aging and melting

Glacial mass balance of Austre Brøggerbreen (Spitsbergen), 1971–1999, modelled with a precipitation-run-off model

An energy balance based HBV model was calibrated to the run-off from Bayelva catchment in western Spitsbergen, Svalbard. The model simulated the glacier mass balance, and the results were compared to observations at Austre Brøggerbreen for the period 1971-1997. Even though the model was optimized to observed run-off from a catchment in which the glaciers constitute 50% of the area, and not to the observation of glacier mass balance, the model was able to reconstruct the trends and values of the mass balance found through observations. On average the simulation gave a negative net balance of 696 mm. The observed average is 442 mm. The simulated winter accumulation was in average for the same period 9% lower and the summer ablation 17% higher than the observed. The years 1994-96 show deviations between simulated and observed winter accumulation up to 160%. This can probably be accounted for by extreme rainfall during the winter, leading to thick ice layers which make accurate observations difficult. The higher simulated summer ablation might indicate that the glaciers in the catchment as a whole have a larger negative mass balance than Austre Brøggerbreen. The simulations showed that the glacier mass-balance would be in equilibrium with a summer temperature 1.2°C lower than the average over the last decades or with a 100% increase in the winter (snow) precipitation. These are higher values than former estimates. A combined change of temperature and precipitation showed a synergic effect and thereby less extreme values

Modelling Flash Floods Driven by Rain-on-Snow Events Using Rain-on-Grid Technique in the Hydrodynamic Model TELEMAC-2D

Due to the changing climate, flash floods have been increasing recently and are expected to further increase in the future. Flash floods caused by heavy rainfall with snowmelt contribution due to sudden rises in temperature or rain-on-snow events have become common in autumn and winter in Norway. These events have caused widespread damage, closure of roads and bridges, and landslides, leading to evacuations in the affected areas. Hence, it is important to analyze such events. In this study, the rain-on-grid technique in the TELEMAC-2D hydrodynamic model was used for runoff modelling and routing using input of snowmelt, and precipitation partitioned on snow and rain was calculated via the hydrological model HBV. The results show the importance of including snowmelt for distributed runoff generation and how the rain-on-grid technique enables extracting flow hydrographs anywhere in the catchment. It is also possible to extract the flow velocities and water depth at each time step, revealing the critical locations in the catchment in terms of flooding and shear stresses. The rain-on-grid model works particularly well for single peak events, but the results indicate the need for a time-varying curve number for multiple peak flood events or the implementation of another infiltration model

Grønn energi til Stryn Sommerski - Utredningsstudie om alternative energiløsninger

Strynefjellet Sommerski ligger langt fra kraftnettet, og strømforsyningen er dermed basert på bruk av fossile brensler med årlige CCE-utslipp på ca. 61 tonn. I denne rapporten er tre ulike alternative energiforsyningssystem blitt evaluert: småskala vannkraft, solkraft og framføring av kraftlinje fra Videsæter (6 km). Et lite vannkraftanlegg kommer ut som det beste alternativet med lavest totalkostnad samt minst påvirkning på naturmiljøet. Estimert total nvesteringskostnad ligger på 11, 30 og 20 MNOK for henholdsvis vannkraft, solkraft og framføring av kraftlinje. Det er flere fordeler i bruk av småskala vannkraft ved sommerskisentret. Periodiseringen av tilsiget i elva Videdøla faller sammen med når det er behov for strøm grunnet bresmelting, og for mesteparten av skisesongen er det mer enn nok vann tilgjengelig. I tørre og kalde perioder med lite tilsig vil det oppstå situasjoner da kapasiteten ikke er tilstrekkelig, men leveringssikkerheten kan økes med et lite inntaksbasseng. Alternativt kunne småkraftanlegget kombineres med en brenselcelle for å lagre energi i form av hydrogen, men dette alternativet vil neppe være lønnsomt. Vannkraftanlegget vil bygges nær eksisterende infrastruktur, noe som vil minimere inngrepet i naturmiljøet

Grønn energi til Stryn Sommerski - Utredningsstudie om alternative energiløsninger

Strynefjellet Sommerski ligger langt fra kraftnettet, og strømforsyningen er dermed basert på bruk av fossile brensler med årlige CCE-utslipp på ca. 61 tonn. I denne rapporten er tre ulike alternative energiforsyningssystem blitt evaluert: småskala vannkraft, solkraft og framføring av kraftlinje fra Videsæter (6 km). Et lite vannkraftanlegg kommer ut som det beste alternativet med lavest totalkostnad samt minst påvirkning på naturmiljøet. Estimert total nvesteringskostnad ligger på 11, 30 og 20 MNOK for henholdsvis vannkraft, solkraft og framføring av kraftlinje. Det er flere fordeler i bruk av småskala vannkraft ved sommerskisentret. Periodiseringen av tilsiget i elva Videdøla faller sammen med når det er behov for strøm grunnet bresmelting, og for mesteparten av skisesongen er det mer enn nok vann tilgjengelig. I tørre og kalde perioder med lite tilsig vil det oppstå situasjoner da kapasiteten ikke er tilstrekkelig, men leveringssikkerheten kan økes med et lite inntaksbasseng. Alternativt kunne småkraftanlegget kombineres med en brenselcelle for å lagre energi i form av hydrogen, men dette alternativet vil neppe være lønnsomt. Vannkraftanlegget vil bygges nær eksisterende infrastruktur, noe som vil minimere inngrepet i naturmiljøet

Grønn energi til Stryn Sommerski - Utredningsstudie om alternative energiløsninger

Strynefjellet Sommerski ligger langt fra kraftnettet, og strømforsyningen er dermed basert på bruk av fossile brensler med årlige CCE-utslipp på ca. 61 tonn. I denne rapporten er tre ulike alternative energiforsyningssystem blitt evaluert: småskala vannkraft, solkraft og framføring av kraftlinje fra Videsæter (6 km). Et lite vannkraftanlegg kommer ut som det beste alternativet med lavest totalkostnad samt minst påvirkning på naturmiljøet. Estimert total nvesteringskostnad ligger på 11, 30 og 20 MNOK for henholdsvis vannkraft, solkraft og framføring av kraftlinje. Det er flere fordeler i bruk av småskala vannkraft ved sommerskisentret. Periodiseringen av tilsiget i elva Videdøla faller sammen med når det er behov for strøm grunnet bresmelting, og for mesteparten av skisesongen er det mer enn nok vann tilgjengelig. I tørre og kalde perioder med lite tilsig vil det oppstå situasjoner da kapasiteten ikke er tilstrekkelig, men leveringssikkerheten kan økes med et lite inntaksbasseng. Alternativt kunne småkraftanlegget kombineres med en brenselcelle for å lagre energi i form av hydrogen, men dette alternativet vil neppe være lønnsomt. Vannkraftanlegget vil bygges nær eksisterende infrastruktur, noe som vil minimere inngrepet i naturmiljøet.publishedVersio

The Story of a Steep River: Causes and Effects of the Flash Flood on 24 July 2017 in Western Norway

Flash floods can cause great geomorphological changes in ephemeral fluvial systems and result in particularly severe damages for the unprepared population exposed to it. The flash flood in the Storelva river in Utvik (western Norway) on 24 July 2017 was witnessed and documented. This study assessed the causes and effects of the 2017 flood and provides valuable information for the calibration and validation of future modelling studies. The flooded area at peak discharge, maximum wetted and dry areas during the entire event, critical points and main flow paths were reconstructed using on-site and post-event (i) visual documentation, such as photographs and videos, and (ii) aerial surveying, such as orthophotographs and laser scanning, of the lowermost reach. The steep longitudinal slope together with the loose material forming the valley and riverbed contributed to a large amount of sediment transport during this extreme event. Steep rivers such as the Storelva river have very short response times to extreme hydrologic conditions, which calls for exhaustive monitoring and data collection in case of future events, as well as modelling tools that can emulate the hydro-morphodynamics observed during events such as the 2017 flash flood