Location: Water Management and Systems ResearchTitle: Urbanization of grasslands in the Denver area affects streamflow responses to rainfall events
|WILSON, STACY - Colorado State University|
|BHASKAR, ADITI - Colorado State University|
|CHOAT, BENJAMIN - Colorado State University|
|KAMPF, STEPHANIE - Colorado State University|
|HOPKINS, KRISTINA - Colorado State University|
Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2022
Publication Date: 10/3/2022
Citation: Wilson, S., Bhaskar, A.S., Choat, B., Kampf, S.K., Green, T.R., Hopkins, K.G. 2022. Urbanization of grasslands in the Denver area affects streamflow responses to rainfall events. Hydrological Processes. 36(10). Article e14720. https://doi.org/10.1002/hyp.14720.
Interpretive Summary: Streamflow responses to rainfall events may be affected by urbanization. This study in the Denver area of Colorado, USA found that streamflow in watersheds with higher fractions of impervious areas, such as pavement, were produced at lower precipitation thresholds. On average, streamflow events in this semi-arid climate responded faster and with higher peak flows in watersheds having more imperviousness. This work highlights the need for local adaptation of stormwater management to mitigate the effects of streamflow changes with urbanization.
Technical Abstract: A thorough understanding of how urbanization affects stream hydrology is crucial for effective and sustainable water management, particularly in rapidly urbanizing regions. This study presents a comprehensive analysis of changes in streamflow response to rainfall events with urbanization in the semi-arid area of Denver, Colorado, USA. We used eight years of April to October instantaneous streamflow data in 21 watersheds ranging in size from 1 to 90 km2 with impervious areas ranging from 1% to 47%. With these data, we applied a semi-automated method to identify a total of 2,877 streamflow events, which we analyzed for event-based metrics of peak flow, runoff depth, runoff ratio, time to peak, duration, and number of streamflow events occurring in response to rainfall events. We also determined whether streamflow response could be predicted by a precipitation threshold. The more impervious watersheds had a precipitation threshold of 1-2 mm/hr needed to produce a streamflow response, compared to thresholds of 4-36 mm/hr for watersheds with less than 10% impervious surface cover. This lower precipitation threshold in more impervious watersheds led to more frequent streamflow responses. On average, streamflow events had shorter duration and higher peak flows in watersheds with more impervious surface cover. Runoff depth, runoff to rainfall ratio, and time to peak either gave mixed results or did not vary significantly with imperviousness. These alterations in streamflow response to rainfall events indicate the specific ways that urban development changes how streams respond to rain events in a semi-arid setting. This work points to the need for local adaptation of stormwater management to mitigate the effects of streamflow changes with urbanization.