Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
Geology Don't get GSW? Talk to your librarian.
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Geology; July 2003; v. 31; no. 7; p. 569-572; DOI: 10.1130/0091-7613(2003)031<0569:SAODRA>2.0.CO;2
© 2003 Geological Society of America
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Magilligan, F. J.
Right arrow Articles by Graber, B. E.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Scale-independent assessment of discharge reduction and riparian disconnectivity following flow regulation by dams

Francis J. Magilligan*,1, Keith H. Nislow*,2 and Brian E. Graber*,3

1 Department of Geography, Dartmouth College, Hanover, New Hampshire 03755, USA
2 U.S. Department of Agriculture Forest Service, Northeastern Research Station, Amherst, Massachusetts 01003, USA
3 Watershed Restoration Specialist, Madison, Wisconsin 53703, USA

By using the established hydraulic relationships among flood frequency, flood magnitude, and river-channel capacity, we develop a scale-independent assessment of the hydrogeomorphic impacts of 21 dams across the United States that have broad ranges in function and contributing drainage area. On the basis of generalized extreme value (GEV) analysis of pre- and post-dam hydrologic records, our analysis indicates that the 2 yr discharge has decreased ~60% following impoundment, exceeding the magnitude of climatically triggered discharge reductions occurring during the Holocene. Reductions in the frequency of the pre-dam 2 yr discharge have been equally profound. The pre-dam 2 yr flood has occurred on average twice per site, whereas statistical analysis indicates that it should have occurred ~20 times. Furthermore, floods greater than bankfull have been essentially eliminated by dams, completely disconnecting the riparian zone from riverine influence. Our analyses herein suggest that a critical threshold of disconnectivity exists and corresponds approximately to the pre-dam 5 yr flood. This similar recurrence probability exists independent of region, dam type, or catchment size.

Key Words: dams • hydrologic regime • floods • riparian






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2009 by Geological Society of America