Theoretical relationships between rainfall intensity and kinetic energy variants associated with stormwater particle washoff

Brodie, Ian and Rosewell, Colin (2007) Theoretical relationships between rainfall intensity and kinetic energy variants associated with stormwater particle washoff. Journal of Hydrology, 340 (1-2). pp. 40-47. ISSN 0022-1694

Abstract

Previous studies have identified rainfall intensity as a contributing factor to the amount of suspended particles washed from urban areas during storms. Moreover, it has been postulated that the square of rainfall intensity (I 2) provides a measure of the rainfall kinetic energy (KE) available for washoff processes. This paper provides a theoretical analysis of the potential inter-relationships between I 2 and rainfall KE. A hypothetical raindrop size distribution (DSD) was used to derive rainfall energy characteristics. A special form of the Marshall-Palmer DSD was developed that ensured conservation of rainfall mass over the analyzed range of rainfall intensities. This ‘conserved rainfall mass’ DSD was used to calculate the specific KE variants of rainfall (the time-specific KEI and the volume-specific KEP). It was found that KEI has a loge-based relationship with rainfall intensity. Empirical relationships widely used in soil erosion studies have generally adopted a log10 basis. A direct relationship between the two KE variants and I2 appears to be absent. A new KE variant (KEIA) is proposed and it is demonstrated that this variant supports the hypothesis that I2 is a measure of the KE of rainfall. KEIA is the kinetic energy potentially transferred from raindrops to the proportion of the unit area impacted at a specific instant in time. It is a function of KEI and raindrop circumferential area. Relationships based on variants of rainfall momentum M are also investigated. The relationship between MI and KEI is nearly linear as a fitted power function has an exponent close to unity (equal to 0.93). This suggests KE and M could be effectively interchangeable if used in particle washoff estimation.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Accepted version deposited in accordance with the copyright policy of the publisher.
Depositing User: Mr Ian Brodie
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Date Deposited: 13 Nov 2007 23:24
Last Modified: 02 Jul 2013 22:47
Uncontrolled Keywords: rainfall kinetic energy; momentum; stormwater; particle washoff; drop size distribution
Fields of Research (FOR2008): 04 Earth Sciences > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology
09 Engineering > 0905 Civil Engineering > 090508 Water Quality Engineering
09 Engineering > 0905 Civil Engineering > 090509 Water Resources Engineering
Socio-Economic Objective (SEO2008): E Expanding Knowledge > 97 Expanding Knowledge > 970109 Expanding Knowledge in Engineering
Identification Number or DOI: doi: 10.1016/j.jhydrol.2007.03.019
URI: http://eprints.usq.edu.au/id/eprint/2826

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