Floodplain Development, El Niño, and Cultural Consequences in a Hyperarid Andean Environment

Bibliographic Data

ID8378010
AuthorsR B Manners, R Manners (University of North Carolina at Chapel Hill), Francis J Magilligan (0000-0002-0082-5526, Dartmouth College), P S Goldstein (0000-0002-4431-6731, University of California San Diego)
Year2007
Volume97
Issue2
Pages229-249
Publication date2007-06-01
Peer ReviewedYes
Open AccessNo
TypeARTICLE
VenueAnnals of the Association of American Geographers (JOURNAL)
Journal identifiersISSN: 0004-5608 • E-ISSN: 1467-8306
PublisherInforma UK Limited (PUBLISHER • GB)
DOI10.1111/j.1467-8306.2007.00533.x
OpenAlexW2124647100
LanguageEN
Citations received17
References cited71

Using field-mapping, remote-sensing (ASTER, aerial photography), and GIS/GPS, we identified and analyzed reach-scale geomorphic responses to contemporary floods along a 20-km valley length in hyperarid southern Peru. We combined these data with alluvial stratigraphy of remnant terrace patches recording late Holocene aggradation and incision. In this manner we ascertained how climate change, especially the occurrence of the El Niño–Southern Oscillation (ENSO), affects the magnitude and frequency of large floods at mid-elevations of southern Peru's Atacama Desert, and we documented the geomorphic effects of large floods on stream channel properties, especially the large-scale floodplain erosion and channel enlargement occurring during these large ENSO-related floods. Reach-averaged channel widening of ∼30 m occurs during large ENSO-related floods, with floodplain erosion rates of 2 ha/river km commonly occurring. Recovery occurs in two stages: channel narrowing requires several decades of lateral bar development which can ultimately aggrade sufficiently for complete floodplain development to occur. There was a similar response to ENSO floods during the late Holocene, and our radiocarbon dating of alluvial surfaces, combined with an ASTER-DEM of the floodplain, indicates that ∼80 percent of the floodplain is younger than at least 550 14C years. We conclude that the lateral erosion and recovery cycle related to ENSO floods could have been a critical factor for prehistoric societies dependent on floodplain agriculture. If cultural systems can maintain pace with geomorphic change in these irrigated floodplain systems, the loss of arable land may not be critical. However, severe social stresses may result if episodes of accelerated floodplain loss outpace both natural recovery and social adaptation

Aggradation · Alluvial plain · Alluvium · Archaeology · Channel (broadcasting) · Erosion · Flood myth · Floodplain · Fluvial · Geography · Geomorphology · Holocene · Hydrology (agriculture) · Overbank · Physical geography · Structural basin · Tributary · Geology · Geology and Paleoclimatology Research · Hydrology and Sediment Transport Processes · Oceanography · Paleontology · Tree-ring climate responses

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