Lower Mississippi River Environmental Program. Report 15. Vegetation Development on Revetments Along the Lower Mississippi River

Nearly 900 miles of bank protection works (revetments) are in place along the Lower Mississippi River. These structures are composed of a variety of materials and support various degrees of vegetation cover. Plant establishment on revetted banks has implications for both bank stability and wildlife habitat quality; therefore, a study was initiated to investigate the relationship between vegetation development and revetment features and materials. Field sampling at 25 sites indicated that vegetation development was more pronounced on upper than lower banks and on sites protected from direct impacts of high- velocity flows. Loose rock paving (riprap), which is typically employed on upper banks, generally supported the most vegetation. Plants were frequently found growing between the blocks of articulated concrete mat revetments. Asphalt paving had high herbaceous cover, but tree establishment was limited. In general, only two species of trees (Salix nigra and Salix interior) commonly occurred on the lower half of revetted banks. Upper banks and the top bank zone supported a more diverse tree species assemblage. Vines were a major component of revetment plant communities on the upper bank. Ground cover vegetation was more abundant in higher bank zones, but many annual species were able to colonize the lower bank where sediment was deposited as the river receded.