The geography and geomorphic development of Gifford Point near Bellevue, Nebraska

Anthropogenic influences frequently produce more lasting effects on the landscape than natural forces (Hook, 1994). Many areas of the world have been altered to accommodate human needs. Throughout history, rivers have been diverted or dammed in attempts to provide safe travel routes, irrigation, or energy. Gifford Point is as much a product of human forces - the need for a stable, navigable waterway - as it is of the Missouri River from which it was originally formed. This study explores the factors contributing to geomorphic changes to the point during the past 100 years with emphasis on anthropogenic changes resulting from river stabilization in the 1930s. The main question posed for this study was: What geomorphic changes were produced by United States Army Corps of Engineers river channelization work and how did these changes compare to Gifford Point\u27s pre-stabilization geomorphology? This study explored the factors contributing to that geomorphic change. The problem was approached by visually interpreting historical material such as maps, satellite imagery, and aerial photographs to determine the geomorphology prior to and after river stabilization. Substrate and dendrochronological samples obtained from an area of the point which had undergone stabilization work, along with field checks and interviews were used to verify information obtained from historical material. The shift of Gifford Point from a northeast-southwest orientation in the early 1800s to its current east-west position was illustrated by overlaying a series of historical maps (1851 - 1975). Aerial photographs (1938, 1972, and 1982) and a 1985 Landsat Thematic Mapper (TM) image provided information regarding landcover and geomorphic changes resulting from the United States Army Corps of Engineers (USACE) river channelization work, farming, and logging operations. Substrate samples provided a picture of the point\u27s geologic structure and flood history. Dendrochronology played a key role in estimating when surfaces of the point stabilized above the mean-annual-ffow level and, along with historical material, helped delineate the most stable area of the point. Results indicate that anthropogenic processes have produced the most substantial changes during the past 100 years. The results also suggest that tree age corresponds well with point stabilization and can be used to estimate when surfaces first reach an elevation above-mean-annual flow. This study also provides the ground work for more selective studies of the processes affecting the point\u27s morphology