Documentation of Risvollan Urban Hydrological Research Field, 2011
Master thesis
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https://hdl.handle.net/11250/2983118Utgivelsesdato
2012Metadata
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Sammendrag
Risvollan urban hydrology research field is a field laboratory located in Trondheim city, Sør-Trøndelag County in Norway. The field includes a main catchment, and an urban hydrological station. The field has also a small rain garden recently added nearby the main catchment in 2010. The station is located downstream at the end of the main catchment. It is capable of measuring parameters such as storm water- and wastewater flow, short duration precipitations, snowmelt intensity, air- and ground temperature, air humidity, short wave radiation and wind speed/direction. Since 1986, the field has worked as a research laboratory for dozens of projects such as several semester, master and PhD thesis, as well as scientific articles and reports. To mention a few of their topics, some theses focused on flooding analysis, pollution control, bio retention, urban runoff modeling, LID solutions, open storm water management, surface analysis, anthropogenic effect on snow melting, climate change and uncertainty of rainfall- and urban modeling. Almost from the beginning of the operational time, Risvollan station has been able to collect qualified data on central parameters necessary to complete a hydrologic balance model for the catchment. Recently (2010 and 2011), the station has been upgraded by installations of new instruments together with new data transmission system. The main catchment has during the autumn of 2011 been developed by the construction of 27 new apartments at the downstream end nearby the station. It was not expected that these changes would give significant impact on the amount of surface runoff. However, it was necessary to carry out an updated description of the catchment and to investigate how the properties may affect the hydrological conditions. It was also important to perform a detailed documentation of the current measurement equipments, along with their capacities/limitations. Detailed analyses and discussions of recently measured data would be carried out to control the performance of the new instruments, and to investigate the trends in rainfall/runoff characteristics of the catchment. The documentation of the research field would comprise preparation for model analyses, and a presentation of the outcome of this. The purpose with this thesis was to carry out these tasks so that it would be possible to get a clear picture of the current status and function of the research field.
The thesis provided a clear overview of the current conditions of the research field. However, it also revealed how uncertain some of the catchment properties could be, and the degree of validity for some of the instruments at the station. There were also uncertainties surrounding some of the pipe dimensions of the storm water network. In detail, the most important findings were:
• The hand drawn outer field boundary was considered to be partially valid. The watershed analyses performed in ArcMap generated catchments that were very similar to it.
• The comparison between the precipitation gauges showed that the newly installed Geonor gauge didn’t provide realistic precipitation data between May and November 2011.
• The main catchment’s total infiltration capacity was estimated to be approximately 5 mm.
• The statistical calculations of historical precipitation data showed that the annual amount of precipitation had slightly increased since 1986 (1.6 – 2.7 %).
• The determination of surface characteristics by the use of geo referred satellite images in ArcMap was considered to be valid.
• The runoff model developed in PCSWMM was considered to be realistic. It was easy to calibrate it, and it had almost the same appearance as the runoff model developed by DHI.