“EVALUATION OF EFFECTIVENESS OF STREAMBANK STABILIZATION PRACTICES AND FLOOD IMPACT ON CEDAR RIVER, NEBRASKA”

Advisor: Dr. Aaron Mittelstet

Stream restoration has been a major environmental objective for preserving biodiversity, reducing loss of valuable cropland and improving water quality. The impact and efficiency of streambank stabilization practices has been simulated using erosion-prediction models; however, evaluation of the erosion-control practices to measure their efficiency is often neglected. This project monitored changes in fluvial geomorphology on Cedar River, Nebraska and quantified the effectiveness of 18 sites with streambank stabilization practices. A flood event in 2010 due to dam failure acted as a major parameter in measuring the efficiency of the erosion control practices. The methodology included aerial imagery to measure streambank migration over time. Flow data, cross-sectional surveys, radius of curvature of meanders and vegetation density were documented to determine their influence on streambank erosion. Jetties were observed to be the most cost effective under moderate flow conditions, but three out of ten sites failed during the flood event. Erosion rates were significantly higher during the flood, especially immediately downstream of the failed dam. Radius of curvature and riparian vegetation did not impact the erosion rate significantly during or before the flood event. Other factors like local site conditions, root depth and soil type may be more dominant in impacting streambank in this stream system.