Investigation of precipitation throughfall patterns beneath urban tree canopies: An exploration of precipitation re-direction and implications for stormwater management
Abstract
The potential for vegetation in urban environments to modulate the generation of runoff from precipitation has become a topic of increasing importance. The incorporation of formal green infrastructure including bioswales, rain gardens and permeable pavement into urban neighbourhoods has been identified as beneficial for the management of stormwater runoff. Among many urban settings, trees are also a form of green infrastructure that can influence runoff generation. However, the ways in which the canopy changes stormwater runoff remain less understood. Canopy architecture and density may influence interception storage and redirect water to particular portions of the sub-canopy. A study located in central Wisconsin was performed in the summer of 2019 to investigate spatial patterns of throughfall beneath urban trees under precipitation events of various magnitudes and determine the influence of canopy structure on throughfall patterns. Data collection occurred around three representative street trees located in Fond du Lac Wisconsin. Spatial throughfall data were gathered via a series of collection buckets (64) spaced in a grid pattern beneath the canopy of each tree prior to the onset of precipitation. To quantify canopy density in relation to throughfall, digital photographs were taken at zenith directly above each container to estimate canopy cover. Additionally, Plant Area Index (PAI) was estimated from digital photographs taken beneath the canopies of each tree with a 180° hemispherical lens. Canopy architecture in relation to collection buckets was estimated via structure from motion analysis of digital photographs (~ 200 - 300) of the canopy. Results indicate that each canopy has a unique threshold for precipitation storage related to size and leaf density. Once the interception storage capacity is exceeded, throughfall patterns closely follow branch and limb location. This observation can be explained as a "funnelling" effect by large limbs as water falls into the sub-canopy. This work helps to illuminate the role of canopy architecture on precipitation interception and throughfall within an urban environment within the larger context of urban trees and stormwater management.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H23Q2140A
- Keywords:
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- 1813 Eco-hydrology;
- HYDROLOGY;
- 1834 Human impacts;
- HYDROLOGY