Graduation Year

2023

Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts

Department

Environmental Analysis

Reader 1

Charlotte Chang

Reader 2

Char Miller

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© 2022 Naomi I Meurice

Abstract

Beaches in Southern California are highly recreated by residents and visitors, making beaches socially and economically important. Public health departments in coastal communities are in charge of measuring water quality and ensuring it is safe for users. Research in the past has indicated that beach water quality gets worse after storms, with bacteria levels jumping on the day of a storm and staying high for up to five days. Studies have shown these spikes in bacteria to be associated with storm runoff, with beaches closer to runoff discharge locations experiencing more impact. However, prior research has not considered the period of dryness before a rain event and how that may impact beach water quality. For this research, I analyzed the impacts of the number of days without rain prior to a rain event, to see if this period of dryness influences the water quality for the day that it rains and the following five days. I performed a multiple linear regression to assess the relationship between water quality and days without rain, days since rain, and beach location, and found all three variables of interest to be statistically significant. Bacterial levels reach their peak on the day that it rains, and drop as time goes on. Following a longer period of dryness, bacterial levels after a rain event start higher, and thus take longer to reduce to safe levels. Given this information, coastal public health departments should automatically post signage following rain events that are preceded by long dry periods, which informs beach-goers that the water is likely unsafe to enter. In addition, county officials should consider potential projects to limit the amount of untreated stormwater that flows into the ocean. These projects could include stormwater capture or the treatment of water before discharging into the ocean.

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