Shifting BEC Zones

Climate change, caused mainly by human activities, is impacting the world's ecosystems, including terrestrial ecosystems, through changes in temperature and precipitation. Biogeoclimatic (BEC) zones are a classification system used for ecosystem management in British Columbia that divides the region into different zones based on climate, soil content, and associated plant communities. For example, UBC’s current BEC zone is CWHxm1, which stands for Coastal Western Hemlock Zone, very dry, maritime, southern, coastal subzone. Green infrastructure, which includes natural solutions like forests, parks, and green roofs, can help mitigate the impacts of climate change by improving water quality, reducing flooding impacts, and increasing human health. UBC is taking action to improve its climate resilience, including developing adaptation strategies and creating green building plans. The Shifting Biogeoclimatic (BEC) Zones project aims to understand how shifting precipitation patterns will affect green infrastructure management at UBC's Point Grey campus in Vancouver, Canada. This research is important because it will help UBC plan for the impacts of climate change and create more resilient and sustainable infrastructure.

The study site of the Shifting BEC Zone project is the University of British Columbia Vancouver campus, BC, Canada. The land of the UBC Vancouver campus once belonged to the ancestral and unceded land of indigenous people (UBC, 2021). UBC Vancouver campus is located in a temperate rainforest of the southwestern coastal areas of BC, and the climate of this study site is mild oceanic climate, with cool summers and mild winters. Moderate climate helps with the growth of various types of vegetation, species, and landscapes. UBC campus land cover could be divided into three general types: 30.4% tree canopy, 25% soft landscape (shrubs and tree understorey included), and 44.6% artificial surfaces that do not have vegetation (UBC, 2021).

This study utilizes data on mean daily, monthly, and yearly precipitation totals for winter and summer from historical climate data in Vancouver. However, some of the data was limited, so using data from other nearby climate stations to fill in the gaps. I pre-processed the data by making necessary corrections to ensure accuracy and collected data from 1901 to 2021. Since stormwater management is the main focus of this investigation, the project is focusing more on the rainy season.

Historical climate data from the Vancouver UBC campus has been collected to analyze the trend of climate change. Specifically, the focus is on the total monthly precipitation and seasonal precipitation for the winter and summer rainy seasons from 1901 to 2022. The assumption is that climate change might follow certain patterns and models, and I will evaluate several climate models for predicted climate until 2100 using Climate BC v7.30. The Bias Corrected SSP2.45 model is selected for future climate analysis, as it fits better with the historical trend and is considered moderate compared to other models. By comparing the Intensity-Duration-Frequency (IDF) curves provided by various sources, the team will determine the relationship between the intensity and frequency of rainfall and the predicted possibility of future precipitation in a certain duration. This information will be valuable for managing stormwater and planning for future climate change impacts. It is important to note that the team assumes stationarity, which means that variations in data are caused by random fluctuations and are independent of any system changes.

To analyze the stormwater event, I first calculate the velocity of the water flow at the UBC campus. Soil permeability, slope, and flow accumulation were considered as factors that can influence the velocity.  Soil data  and  UBCGeodata  were used to classify permeable and impermeable surfaces, as well as water features. The slope was generated using  UBC DEM data  in ArcGIS Pro. Based on the hypothesis that the flow velocity is affected by spatial components and surface types, and flow velocity does not change over time at a certain location, we can create a velocity field of UBC water flow. Next, to determine an estimated time for discharge, predicted precipitation from climate analysis was used. The 18 mm value of precipitation is selected, not only indicative of the average and median difference between historical and future precipitation for a 24-hour storm event across all return periods but also represents the predicted precipitation values for many other scenarios, such as a 30-minute storm event in a 50-year return period. Therefore, precipitation duration and discharge time were compared to evaluate the effectiveness of the UBC drainage system. Instantaneous discharge reaching the drain can be calculated since there is only one drain in the northern part of the UBC Vancouver campus. 

Combining the impervious classification, water flow velocity, and rain flow time, potential areas of concern or risk for stormwater management were identified. Areas with low flow velocity may be more susceptible to flooding, while areas with high impervious surface coverage can increase the volume of runoff during storms, potentially overwhelming the capacity of the drainage system and leading to flooding. Areas near sensitive environments can also be more prone to environmental damage if stormwater is not properly managed. By using various data sources and tools, this analysis will help to identify areas of concern and inform the development of effective stormwater management strategies.

The analysis of precipitation data suggests that both the intensity and amount of rainfall for different durations are increasing, indicating a higher probability of extreme rainfall events in the future. However, the current stormwater management system at UBC may not be equipped to handle such severe weather events.

The Figure suggests areas where stormwater infrastructure improvements may be needed.

This project aimed to analyze the impact of changing precipitation patterns on green infrastructure management at the University of British Columbia (UBC). The study found that UBC's green infrastructure is not designed to handle heavy rainfall events, resulting in flooding and erosion issues. The project suggests several recommendations for UBC's green infrastructure planning and stormwater management, such as balancing permeable and impermeable surfaces, installing and upgrading green roofs and other green infrastructure, monitoring and evaluating climate change factors, and hiring professional people for planning and elevation.

However, the study has some limitations, such as the availability and quality of data, assumptions in calculating velocity and flow time, and the need to incorporate additional factors like soil types. The project provides valuable insights into future green infrastructure planning and stormwater management strategies, not only at UBC but also for other locations facing precipitation changes. The findings underscore the importance of incorporating climate change as a crucial element while considering other design factors in the planning and construction of resilient infrastructure. Policymakers and urban planners need to prioritize effective stormwater management practices that reduce the risk of flooding, protect the environment, and promote sustainable development. They can balance the risks to decide whether infrastructure should be designed for a moderate or high increase in rainfall and consider using more sustainable and integrated approaches to urban stormwater management.