Comprehensive analysis of design storm formulation across Newfoundland and under climate change with scarce data

Amponsah, Abena Owusua (2023) Comprehensive analysis of design storm formulation across Newfoundland and under climate change with scarce data. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (61MB)

Abstract

Urban and rural watersheds are becoming increasingly vulnerable to extreme weather events and their consequences. One such consequence is flooding. Stormwater management systems need to be efficiently designed to handle both the quantity and quality of floodwaters. Efficient stormwater systems can be achieved when design parameters are set to their optimum. The design parameters for proper sizing of stormwater infrastructure are obtained from design storms, a combination of Intensity-Duration-Frequency (IDF) curves and a rainfall temporal distribution. IDF curves are developed using rainfall data; as such, changes to the climate will affect these curves. There is a need to re-evaluate the current design storms to determine how they will be affected by the changing climate. Evaluating a design storm from a chaotic variable such as precipitation is complex, and the variation in climate makes it more complicated. Information on IDF curves is challenging to obtain, especially at locations where precipitation data is lacking or for which there is little data. The focus of this study is the use of models for data generation and analysis of data for appropriate temporal distribution identification. The application of the work in this thesis provides information to guide engineering design and other hydrological studies under climate change. This thesis presents a series of studies that: assess the impact of climate variations on temporal distributions used in design storm analysis; analyzes how these temporal distribution patterns - when combined with other hydrologic factors - can impact mapping for risk of floods, especially under climate change projections, and develops a precipitation disaggregation model. The assessment of temporal distribution variation with climate shows that current temporal distributions being used may result in under- or over-design based on the location of interest and climate condition used, either current climate or future climate projections. It highlights the importance of using the appropriate temporal distribution to justify the conservative design. The temporal distributions identified are taken a step further to determine their interplay with hydrologic loss methods and their impact on mapping for the risk of floods. The outcome shows that the extent of a flooded area is highly sensitive to the temporal distribution and loss method used. A precipitation disaggregation model is also developed by coupling a method-of-fragments model with a crossover operator and applied to meteorological stations at Ruby Line, St. John’s and Corner Brook to generate hourly data from daily data. These stations were chosen to mainly draw attention to the lack of precipitation data across most locations in the province. The results show that the model can generate hourly data statistics similar to that observed.

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