Application of chemostratigraphy of slackwater deposits to enhance paleoflood reconstruction, Rio Salado, Antofagasta Region, Chile

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Danvey C. Walsh (Creator)
Western Carolina University (WCU )
Web Site:
Jerry Miller

Abstract: This thesis reports a study of novel chemostratigraphic methods applied to flood deposit identification/correlation and subsequent paleoflood hydrology and flood frequency analysis in the Rio Salado, Chile. Flood deposit identification at 4 stratigraphic sections and inter-reach correlations are made on the basis of stratigraphic analysis, radiocarbon dating, concentration-depth profile evaluation of trace elements, and discriminant function analysis of trace elements. Concentrations of trace metals were determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Inherent uncertainty and limitations of radiocarbon dating make unit correlation difficult by this method alone. Chemostratigraphic methods including a multivariate statistical approach show promise for improving the delineation and correlation of slackwater flood deposits in the Rio Salado. Flood deposit correlation by these methods is used to determine the discharge that produced a geologically defined water surface profile employing step-backwater methods. Paleoflood analysis is used to extend the time scale of a short systematically measured gaging record (25 years) in order to better characterize flood magnitude-frequency relationships. Analysis is performed on a well preserved record of 10 floods with discharges ranging from 240 to 515 m3s-1. The oldest of these floods dates to the early 1600’s AD. Using only gaging data, the 100 year flood event has a discharge of 856 m3s-1. The gaging data plus paleoflood data indicates the discharge of the 100 year flood event is 429 m3s-1, a reduction of about 50 %. The recurrence interval of the 2001 flood changes from ~40 years based on gaging data only to ~100 years using the gaging data plus the paleoflood data. A comparison to studies for the well documented and widely destructive 2001 Atacama flood indicates floods of this magnitude have a shorter recurrence interval than previously suggested.

Additional Information

Language: English
Date: 2016
Paleohydrology -- Chile -- Antofagasta (Region)
Chemostratigraphy -- Chile -- Antofagasta (Region)
Slackwater deposits -- Chile -- Antofagasta (Region)
Sedimentation and deposition -- Chile -- Antofagasta (Region)
Floods -- Chile -- Antofagasta (Region)
Loa River (Chile)

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