Rainfall intensity bursts and the erosion of soils: An analysis highlighting the need for high temporal resolution rainfall data for research under current and future climates

David Llewellyn Dunkerley

Research output: Contribution to journalArticleResearchpeer-review

10 Citations (Scopus)

Abstract

Many land surface processes, including splash dislodgment and downslope transport of soil materials, are influenced strongly by short-lived peaks in rainfall intensity but are less well accounted for by longer-term average rates. Specifically, rainfall intensities reached over periods of 10-30 min appear to have more explanatory power than hourly or longer-period data. However, most analyses of rainfall, and particularly scenarios of possible future rainfall extremes under climate change, rely on hourly data. Using two Australian pluviograph records with 1 s resolution, one from an arid and one from a wet tropical climate, the nature of short-lived "intensity bursts" is analysed from the raw inter-tip times of the tipping bucket gauges. Hourly apparent rainfall intensities average just 1.43 mm h -1 at the wet tropical site and 2.12 mm h -1 at the arid site. At the wet tropical site, intensity bursts of extreme intensity occur frequently, those exceeding 30 mm h -1 occurring on average at intervals of 1 d and those of 60 mm h -1 occurring on average at intervals of 2 d. These bursts include falls of 13.2 mm in 4.4 min, the equivalent of 180 mm h -1 , and 29 mm in 12.6 min, equivalent to 138 mm h -1 . Intensity bursts at the arid site are much less frequent, those of 50-60 mm h -1 occurring at intervals of ∼1 month; moreover, the bursts have a much shorter duration. The aggregation of rainfall data to hourly level conceals the occurrence of many of these short-intensity bursts, which are potentially highly erosive. A short review examines some of the mechanisms through which intensity bursts affect infiltration, overland flow, and soil dislodgment. It is proposed that more attention to resolving these short-lived but important aspects of rainfall climatology is warranted, especially in light of possible changes in rainfall extremes under climate change.

Original languageEnglish
Pages (from-to)345-360
Number of pages16
JournalEarth Surface Dynamics
Volume7
Issue number2
DOIs
Publication statusPublished - 15 Apr 2019

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