Event scale hydrograph responses highlight impacts of widespread stream burial and urban infrastructure failures. Issue 5 (15th May 2022)

• Record Type: Journal Article
• Authors: Forgrave, Rebecca; Elliott, Emily M.; Bain, Daniel J.
• Is Part Of: Hydrological processes. Volume 36:Issue 5(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-15
• Subjects: buried streams -- hydrograph analysis -- infrastructure -- rainfall–runoff responses -- stormwater -- urbanization; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14584
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Fast hydrologic responses to storms in urban areas are often attributed to high percentages of impervious surfaces; however, another factor affecting urban storm response is channel burial. No previous studies have documented storm event responses in buried streams despite how common stream burial is in urban areas, with some US cities having over 75% of all headwater channels buried. Understanding event dynamics is particularly important as climate change predictions suggest an increase in frequency of high intensity storms and urban flooding. This study used 15‐min precipitation and discharge data over a period of 6.5 years to categorize storm event responses in Nine Mile Run, an urban watershed in Pittsburgh, Pennsylvania where 98% of all channels are buried. Extensive stream burial led to lower watershed retention capacity and resulted in faster storm event responses relative to other urban streams with comparable imperviousness. Additionally, urban water subsidies in the form of sewer overflows, hydrant flushing, or water line breaks can have measurable contributions to flow event responses and result in seemingly unfeasible runoff ratios. This study demonstrates novel watershed runoff responses in systems dominated by subsurface infrastructure, which play a key role in urban water balance. Additionally, this study highlights the fact that stream restoration is not a universal solution to urban stream flashiness because downstream restoration cannot resolve the impacts of upstream burial. Abstract : Many studies have documented that urbanization leads to flashier hydrographs in urban streams compared to rural streams due to rapid routing of runoff from impervious surfaces. These impacts of rapid runoff routing are exacerbated in buried urban streams where hydrographs are even higher and sooner after start of rainfall with no smoothing of individual rainfall pulses.