Increased nonstationarity of stormflow threshold behaviors in a forested watershed due to abrupt earthquake disturbance
<p>Extreme earthquake disturbances to the vegetation of local and regional landscapes could swiftly impair the former hydrologic function, significantly increasing the challenge of predicting threshold behaviors of rainfall–runoff processes as well as the hydrologic system's complexity ov...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://hess.copernicus.org/articles/27/3005/2023/hess-27-3005-2023.pdf |
| Summary: | <p>Extreme earthquake disturbances to the vegetation of local and regional
landscapes could swiftly impair the former hydrologic function,
significantly increasing the challenge of predicting threshold behaviors of
rainfall–runoff processes as well as the hydrologic system's complexity over
time. It is still unclear how alternating catchment hydrologic behaviors
under an ongoing large earthquake disruption are mediated by long-term
interactions between landslides and vegetation evolution. In a well-known watershed affected by the Wenchuan
earthquake, the nonlinear hydrologic behavior is examined
using two thresholds with intervening linear segments. A lower rising threshold (TH<span class="inline-formula"><sub>r</sub></span>)
value (210.48 mm) observed in post-earthquake local landslide regions
exhibited a faster stormflow response rate than that in undisturbed
forest and grassland–shrubland regions, easily triggering huge flash-flood
disasters. Additionally, an integrated response metric pair (integrated
watershed average generation threshold TH<span class="inline-formula"><sub>g−IWA</sub></span> and rising threshold TH<span class="inline-formula"><sub>r−IWA</sub>)</span> with areas of disparate land use,
ecology, and physiography was proposed and efficiently applied to identify
emergent catchment hydrologic behaviors. The interannual variation in the two
integrated hydrologic thresholds before and following the earthquake was assessed to
detect the temporal nonstationarity in hydrologic extremes and nonlinear
runoff response. The year 2011 was an important turning point along the
hydrologic disturbance–recovery timescale following the earthquake, as
post-earthquake landslide evolution reached a state of extreme
heterogeneity in space. At that time, the TH<span class="inline-formula"><sub>r−IWA</sub></span> value decreased by
<span class="inline-formula">∼</span> 9 mm compared with the pre-earthquake level. This is closely
related to the fast expansion of landslides, leading to a larger extension of
variable source area from the channel to neighboring hillslopes, and faster
subsurface stormflow, contributing to flash floods. Finally, we present a
conceptual model interpreting how the short- and long-term interactions between
earthquake-induced landslides and vegetation affect flood hydrographs at
event timescale that generated an increased nonstationary hydrologic
behavior. This study expands our current knowledge of threshold-based
hydrologic and nonstationary stormflow behaviors in response to abrupt
earthquake disturbance for the prediction of future flood regimes.</p> |
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| ISSN: | 1027-5606 1607-7938 |