Preprints
https://doi.org/10.5194/hess-2021-161
https://doi.org/10.5194/hess-2021-161

  29 Mar 2021

29 Mar 2021

Review status: this preprint is currently under review for the journal HESS.

The impact of spatiotemporal structure of rainfall on flood frequency over a small urban watershed: an approach coupling stochastic storm transposition and hydrologic modeling

Zhengzheng Zhou1, James A. Smith2, Mary Lynn Baeck2, Daniel B. Wright3, Brianne K. Smith4, and Shuguang Liu1 Zhengzheng Zhou et al.
  • 1Department of Hydraulic Engineering, Tongji University, Shanghai, China
  • 2Department of Civil and Environmental Engineering, Princeton University, USA
  • 3Department of Civil and Environmental Engineering, University of Wisconsin-Madison, USA
  • 4Department of Earth and Environmental Sciences, City University of New York-Brooklyn College, USA

Abstract. The role of rainfall space-time structure, as well as its complex interactions with land surface properties, in flood response remains an open research issue. This study contributes to this understanding, specifically in small (< 15 km2) urban watersheds. Using a flood frequency analysis framework that combines stochastic storm transposition-based rainfall scenarios with the physically-based distributed GSSHA model, we examine the role of rainfall spatial and temporal variability in flood frequency across drainage scales in the highly-urbanized Dead Run watershed (14.3 km2) outside of Baltimore, Maryland, USA. The results show the complexities of flood response within several subwatersheds for both short (< 50 years) and long (> 100 years) rainfall return periods. The impact of impervious area on flood response decreases with increasing rainfall return period. For extreme storms, the maximum discharge is closely linked to the spatial structure of rainfall, especially storm core spatial coverage. The spatial heterogeneity of rainfall increases flood peak magnitudes by 50 % on average at the watershed outlet and its subwatersheds for both small and large return periods. The results imply that commonly-made assumption of spatially uniform rainfall in urban flood frequency modeling is problematic even for relatively small basin scales.

Zhengzheng Zhou et al.

Status: open (until 24 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-161', Anonymous Referee #1, 07 May 2021 reply
  • RC2: 'Comment on hess-2021-161', Anonymous Referee #2, 09 May 2021 reply

Zhengzheng Zhou et al.

Zhengzheng Zhou et al.

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Short summary
The role of rainfall space-time structure in flood response is an import research issue in urban hydrology. This study contributes to this understanding in small urban watersheds. Combining stochastically-based rainfall scenarios with a hydrological model, the results show the complexities of flood response for various return periods, implying the commonly-made assumption of spatially uniform rainfall in urban flood frequency is problematic even for relatively small basin scales.