From Reducing the Risk of Urban Flooding to Evaluating Changes in Rainfall Patterns and Impacts of Climate Change

Jiang, Albert
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University of Guelph

From precipitation and infiltration to runoff and evaporation, the urban hydrologic cycle (UHC) is comprised of various components, wherein changes in any individual part may affect the entire structure of UHC in the long term. This research studies rainfall retrospectively, which is an essential component in UHC, from assessing its impact on urban stormwater management systems to understanding the root causes of the increasing severity of rainfall events in a novel perspective. The thesis starts with a review which assesses the ‘One Water’ concept in urban flood management. This review highlights the paramount structured thinking about the connection between each dimension within the hydrologic cycle and generating a holistic view of urban water resources security. Following the conceptual review, the application of Low Impact Development (LID) is assessed with a case study in London, Ontario. This dimension demonstrates that the pressure on urban stormwater infrastructure will increase, and continuing, under the impact of climate change. While rainfall conditions (increasing magnitude and frequency) continue to worsen due to climate change, it is imperative and fundamental to evaluate how rainfall has changed over the years with the influence of climate change and make informed predictions on how rainfall patterns will continue to evolve. Instead of analyzing conventional rainfall patterns indicators such as magnitude and frequency, this research employed a novel perspective: the timing of the heavy rainfall events (based on the Annual Maximum Series – AMS) plays a critical role in revealing the range of impacts of climate change. The time of heavy rainfall events occurrence provides overwhelming evidence indicating there are changing rainfall patterns in time-of-year, which is supported by statistical analyses on the mean, variance, and coefficient of variation. This research also explored the relationship between the inter-event time (IET) between rainfall events and the annual numbers of rainfall events (λ) for a series of rainfall data measured from 5min to 12hr and intensities vary from 2 to 24 mm/hr. It shows that the IET between rainfall events is shortening, and the λ is increasing for the majority rainfall durations at various intensities.

Statistical analysis, Water resoureces engineering, Precipitation, Rainfall, Climate change, Annual maximum series, Timing, Time interval, Low impact development, Sponge city, Wastewater-Based Epidemiology, One-water, Hydrologic cycle