Technical note: Long-term persistence loss of urban streams as a metric for catchment classification
<p>Urbanisation has been associated with a reduction in the long-term correlation within a streamflow series, quantified by the Hurst exponent (<i>H</i>). This presents an opportunity to use the <i>H</i> exponent as an index for the classification of catchments on a...
Main Authors: | , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-06-01
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Series: | Hydrology and Earth System Sciences |
Online Access: | https://www.hydrol-earth-syst-sci.net/22/3551/2018/hess-22-3551-2018.pdf |
Summary: | <p>Urbanisation has been associated with a reduction in the long-term
correlation within a streamflow series, quantified by the Hurst exponent
(<i>H</i>). This presents an opportunity to use the <i>H</i> exponent as an index for
the classification of catchments on a scale from natural to urbanised
conditions. However, before using the <i>H</i> exponent as a general index, the
relationship between this exponent and level of urbanisation needs to be
further examined and verified on catchments with different levels of
imperviousness and from different climatic regions. In this study, the <i>H</i>
exponent is estimated for 38 (deseasonalised) mean daily runoff time series,
22 from the USA and 16 from Australia, using the traditional rescaled-range
statistic (<i>R</i>∕<i>S</i>) and the more advanced multifractal detrended fluctuation
analysis (MF-DFA). Relationships between <i>H</i> and catchment imperviousness,
catchment size, annual rainfall and specific mean discharge were
investigated. No clear relationship with catchment area was found, and a weak
negative relationship with annual rainfall and specific mean streamflow was
found only when the <i>R</i>∕<i>S</i> method was used. Conversely, both methods showed
decreasing values of <i>H</i> as catchment imperviousness increased. The <i>H</i>
exponent decreased from around 1.0 for catchments in natural conditions to
around 0.6 for highly urbanised catchments. Three significantly different
ranges of <i>H</i> exponents were identified, allowing catchments to be parsed
into groups with imperviousness lower than 5 % (natural), catchments with
imperviousness between 5 and 15 % (peri-urban) and catchments with
imperviousness larger than 15 % (urban). The <i>H</i> exponent thus represents
a useful metric to quantitatively assess the impact of catchment
imperviousness on streamflow regime.</p> |
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ISSN: | 1027-5606 1607-7938 |