ASSESSMENT OF THE GEOMORPHIC EFFECTS OF LARGE FLOODS USING STREAMGAGE DATA: THE 1951 FLOODS IN EASTERN KANSAS, USA

Data from 23 U.S. Geological Survey (USGS) streamgages were analyzed to assess the geomorphic effects (short-term change and subsequent recovery) of the record 1951 floods on streams in eastern Kansas. Flood-related, channel-bed elevation change was indicated for 17 gage sites, with substantial deposition at five sites and substantial erosion at two sites. An assessment of post-flood bed elevation recovery was possible for several sites. While recovery to pre-flood channel-bed elevation occurred over a period of months to years at some sites, at other sites recovery was incomplete or absent. Flood-related channel widening with partial recovery was indicated for one site and possible channel widening was indicated for two sites. It was demonstrated that an analysis of streamgage data is a potentially useful technique for assessing the geomorphic effects of a large flood at a site, provided that the gage has a long period of record and is located on an alluvial channel. In the absence of other lines of evidence, streamgage data can provide an estimate of the direction and magnitude (net) of geomorphic change that otherwise might not be available or attainable.