Bren School OF ENVIRONMENTAL SCIENCE & MANAGEMENT University of California, Santa Barbara

Presents

Prof. Nicholas Pinter

Department of Geography

Southern Illinois University

Wednesday, March 16^th 2005

12:00-1:00 p.m. Bren Hall 1424

Flood Magnification on engineered rivers: Contrasting results from the U.S. and European rivers

Large floods in recent years have led to the suggestion that these events have been magnified by human activities. A major obstacle to rigorously testing this hypothesis is that anthropogenic and natural hydrologic changes occur simultaneously and are often indistinguishable. This paper uses a combination of statistical tests to isolate the impacts of upstream mechanisms and instream mechanisms on flooding over the past 100-200 years on the Mississippi and Rhine river systems. On the Mississippi system, statistically significant changes in flood magnitudes and frequencies were identified at 10 of 14 stations, with all but one exhibiting flood worsening. On the Rhine River, significant change occurred at only 1-2 stations. Stage trends reflect all cumulative impacts on flooding, whereas specific-gage analysis isolates changes exclusively from instream mechanisms. Specific-gage results show declining flow conveyance at all stations where flood worsening occurred. Some increases in flood-producing precipitation are detectable, but channel and floodplain engineering has dominated flood-occurrence shifts on both rivers. Compared with the industrialized Mississippi channel, navigation infrastructure on the Rhine apparently has not degraded the river’s capacity to convey flood flows efficiently.