Evaluating the potential stormwater retention of a living retaining wall system

Redesigning standard revetment or retaining walls to capture stormwater could increase the use of living walls and, thus, expand their beneficial impacts, including greening underutilized space. This study evaluated the potential stormwater retention and percent plant coverage of an experimental wall surface for six treatments (five vegetated Sedum treatments and an unplanted ‘control’ wall) on 18 circular living retaining wall systems designed from a standard retaining wall system. Percent stormwater retention, which compared effective precipitation volumes with stormwater runoff volumes, was quantified for 81 storm events from July 2010 to September 2011. Living retaining wall systems planted with S. (Phedimus) takesimensis retained stormwater more effectively than the unplanted wall and other planted treatments, including walls planted with S. spurium, mixed Sedum species, and S. kamtschaticum. Plant surface coverage of the living retaining wall system was the greatest when planted with mixed Sedum species, S. spurium, and S. kamtschaticum. Overall this study demonstrates that properly designed living retaining wall systems may be able to be used as a best management practice for stormwater retention in urban areas. Further study could determine the performance of living retaining walls with a more conventional design (i.e., single aspect vs. four aspects against a slope), over a longer time period, walls planted with other vegetated treatments, and walls featuring different fill and plant materials.