Hydrologic Analysis of Rain Garden Performance

Abstract

Urban flooding became a significant issue for many cities worldwide due to rapid urbanization and increased impervious areas over the past two decades ([1]). Rain gardens are considered to be an economically-friendly solution for addressing this extensive urban storm water problem. The Marlborough neighborhood, in an urban (and older) area of Kansas City, MO (USA) was selected as a large study area with dense rain garden construction opportunities and applicability. The City of Kansas City introduced the rain garden project into this neighborhood to see if the rain gardens could perform well in reducing inflow to the collection system, thus reducing combined sewer system and long-term performance of rain gardens. There are seven rain gardens (part of 135 rain gardens in this six block neighborhood) that were monitored by the UMKC research team. The monitoring data reveals that the seven rain gardens have different performance responses during the same rain event. There are many candidate factors which may affect rain gardens’ hydrological performance, such as watershed area, street slope, watershed slope, impervious area, precipitation depth, precipitation duration peak precipitation intensity, and antecedent dry day. There were a total 57 rain events that were captured capacity issues. Regular and ongoing system monitoring is needed to quantify design parameters between June 2012 and June 2014 for seven monitored locations. This study presents which factors are the most significant to affect the gardens’ hydrological performance for future design. Therefore, a data-driven PCA and MLR model was developed from this study. Internal and external data validation have been processed to assess this model. Future site monitoring and design recommendation have been identified. Rain gardens’ hydrology characteristics research has been done for many years by different research groups nationwide. However, few studies show the detailed rain garden performance characteristics based on actual and varying field data. Most studies are limited to short monitoring periods and/or only one or two rain gardens. This study results can validate rain gardens’ hydrology features. Thus, it can provide valuable support for future engineering site design guidance and new data analysis approach to research work based on more robust and extensive data.