An Evaluation of Re-vegetation on Streambank Stability and Erosion

An essential, natural process of a stream is the movement of sediment. However, the natural balance of sediment transport in a stream is seldom observed as a result of anthropogenic implications. An urbanizing stream can experience increased erosion rates from impervious surfaces increasing runoff and runoff velocity. Poor riparian vegetation is a top physical habitat stressor along creek corridors, affecting 25% of total stream miles within the nation. Planting and maintaining a native riparian vegetated buffer is a basic, cost effective method used by many successful stream restoration projects for best management practices (BMPs). The study performed analyzed the effectiveness of native revegetation to reduce erosion through different assessments. Two reaches along a moderately erodible section of Geronimo Creek in Seguin, TX were selected. One site was re-vegetated (treatment segment), and the other (control segment) was left in its current condition. The geomorphology of the stream evolved from a semi C (2018) to a full G stream (2019) indicating lateral migration. A Bank Erosion Hazard Index (BEHI) was analyzed using a two independent samples t-test resulting in a statistical difference between the treatment and control segment after the approximate 1-year study period. The treatment segment observed 0.68 metric tons of soil loss/year more than the control segment in the bank recession analysis. The average sediment load change for the treatment and control segments were 26% reduction and 50% increase, respectively. The vegetation modified critical shear stress exceeded the average bankfull shear stress by an excess of 4.37 kg/m² meaning that erosion should be reducing as a result of vegetation. Stable vegetation is a fundamental part of the solution for restoration of degrading streams. As concluded by the study of the different assessments used, replanted native vegetation effectively reduces sediment load after approximately one year of study. Two to three more years should be added to the study to better observe reduced erosion and soil load reduction from well-established mature plants as the stream and its banks experience many types of storm frequencies and durations