Persistent Link:
http://hdl.handle.net/10150/185017
Title:
Augmenting flood frequency estimates using flood-scarred trees.
Author:
McCord, Virgil Alexander Stuart.
Issue Date:
1990
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Flood-damaged trees along streams and rivers in 20 localities in Arizona, Colorado, New Mexico, and Utah were examined to assess the feasibility of reconstructing the frequency and magnitude of floods over the last several hundred years. Tree-ring dating of the flood damage produced evidence for 17 floods during the last 125 years, and for at least four floods prior to 1866. Most of the flood-scar dates from the historic period were found to coincide with the dates of major floods on the waterways from which they were collected, or from nearby streams. Flood damage to trees was found to be very abundant and accessible, with the most productive situation probably being that of seasonal streambeds in narrow deep canyons with relatively steep gradients. Amount of effort required to produce a flood chronology appears to be relatively small. Collections at most sites involved sampling from 1 to 5 trees, by extracting 3 to 6 increment cores from each visibly scarred tree, and 2 cores from undamaged trees to facilitate crossdating. At two sites larger collections were made, including 3 cross sections (V-cuts), which were very helpful in establishing dates of scars. For a given channel gradient, scars seem to develop only when the flood depth is above a particular threshold level. This threshold was defined by plotting scar height for scarred trees and flow depth for other floods not producing scars against the logarithm of channel slope. The scarred and unscarred individual points were separated into two well-defined fields, separated by a fairly straight line. Discriminant function analysis showed the separation to be highly significant, and classification of individual points as scarred or unscarred was usually correct. The implication of the scar threshold is that even in drainages with no gage or historical record at all, the presence or absence of flood scars on channelside trees would indicate the occurrence or nonoccurrence of floods of a certain depth over the lifetime of the trees. Basin analysis and field measurements of appropriate channel characteristics would allow this depth and the corresponding discharge to be calculated.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geology
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Baker, Victor R.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleAugmenting flood frequency estimates using flood-scarred trees.en_US
dc.creatorMcCord, Virgil Alexander Stuart.en_US
dc.contributor.authorMcCord, Virgil Alexander Stuart.en_US
dc.date.issued1990en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractFlood-damaged trees along streams and rivers in 20 localities in Arizona, Colorado, New Mexico, and Utah were examined to assess the feasibility of reconstructing the frequency and magnitude of floods over the last several hundred years. Tree-ring dating of the flood damage produced evidence for 17 floods during the last 125 years, and for at least four floods prior to 1866. Most of the flood-scar dates from the historic period were found to coincide with the dates of major floods on the waterways from which they were collected, or from nearby streams. Flood damage to trees was found to be very abundant and accessible, with the most productive situation probably being that of seasonal streambeds in narrow deep canyons with relatively steep gradients. Amount of effort required to produce a flood chronology appears to be relatively small. Collections at most sites involved sampling from 1 to 5 trees, by extracting 3 to 6 increment cores from each visibly scarred tree, and 2 cores from undamaged trees to facilitate crossdating. At two sites larger collections were made, including 3 cross sections (V-cuts), which were very helpful in establishing dates of scars. For a given channel gradient, scars seem to develop only when the flood depth is above a particular threshold level. This threshold was defined by plotting scar height for scarred trees and flow depth for other floods not producing scars against the logarithm of channel slope. The scarred and unscarred individual points were separated into two well-defined fields, separated by a fairly straight line. Discriminant function analysis showed the separation to be highly significant, and classification of individual points as scarred or unscarred was usually correct. The implication of the scar threshold is that even in drainages with no gage or historical record at all, the presence or absence of flood scars on channelside trees would indicate the occurrence or nonoccurrence of floods of a certain depth over the lifetime of the trees. Basin analysis and field measurements of appropriate channel characteristics would allow this depth and the corresponding discharge to be calculated.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeologyen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBaker, Victor R.en_US
dc.contributor.committeememberDean, Jeffrey S.en_US
dc.contributor.committeememberMartin, Paul S.en_US
dc.contributor.committeememberSwetnam, Thomas, W.en_US
dc.contributor.committeememberTelewski, Frank W.en_US
dc.identifier.proquest9024635en_US
dc.identifier.oclc708166730en_US
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