Beyond flashy: assessing rapid chemical and flow event responses in a buried urban stream network in Pittsburgh, PA.
Abstract
During the era of rapid urbanization in the United States in the early 1900s, streamspredominantly headwaterswere rerouted through underground pipes, culverts, and storm drainage networks. This process disconnected surface water from subsurface soil and groundwater storage and also prioritized rapid conductance of runoff from impervious surfaces to downstream locations over infiltration. While past studies of urban streams have documented the relationship between impervious urban landscapes and flashy storm responses, few have highlighted the impact of stream burial or quantified flashiness on an event-scale. This research seeks to characterize the relationship between precipitation and runoff in an urban buried stream network in Pittsburgh, PA, as well as understand how conveyance systems and subsurface interactions affect streamflow and water chemistry during storm events. We couple high frequency in-situ sensor data of nitrate concentration, temperature, conductivity, and discharge with high-frequency, 1-km gridded radar to quantify hydrologic and biogeochemical responses to storm events over a two-year period. Piecewise regression between precipitation depth and runoff yield reveals a precipitation threshold of only 2.8mm needed to generate a runoff response, while lag times as short as 15 minutes from start of precipitation to hydrograph rise demonstrate how rapidly stormwater is conducted downstream in buried channels. Event concentration-discharge relationships highlight how overflowing sanitary and combined sewer pipe networks can subsidize streamflow and create novel chemical responses to storm events. As climate change brings more intense rainfall and more frequent flooding to many U.S. cities with aging infrastructure, understanding these thresholds of runoff generation, flow routing, and contamination from sewer overflows in urban streams is essential to guide infrastructure maintenance, flood mitigation, and water quality management.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H11F..01F