Investigation of effective drainage methods in sports field under various rainfall conditions

Abstract

The starting point of this study is to investigate different techniques and drainage mechanisms of sports fields which takes the attention of big crowds all over the world due to big sports organizations. These type of international sports organizations has social and economic impacts on countries hosting these events. Therefore, drainage of sports fields under various rainfall conditions is a very crucial engineering issue to be investigated. The first goal of the two main purposes of the thesis is to investigate the optimum thickness and particle size gradation of the drainage layer which is consisted of rootzone-sand- and gravel, the second goal is to determine the behaviors of different constant rainfall intensities and durations under which a sporting event can be performed comfortably without any ponding on the surface of the turf and without deteriorating turf quality required for sports events. This study has both experimental and modeling portions. An experimental setup (rainfall simulator and drainage tanks) was developed and calibrated to model the field conditions of sports fields under critical rainfall duration and intensity. Experimental rainfall hyetographs for different durations and return periods were also designed. 100 experiments were conducted to investigate hydrological descriptions of unsaturated flow (variable saturated flow) by using multiple packed sports field drainage layers (Pipe Drain (PD), Suspended Water Table (SWT), Sand Groove (SG), and Slit Drain (SD). The hydrograph parameters which are a time to start to drain, maximum outflow, time to reach maximum outflow, and infiltration rate were also evaluated for PD, SWT, SG, and SD. The hyetographs had more distinctive effects on the shape of the drainage outflow hydrographs for PD and SWT. The rainfall intensities were not separately caused to surface ponding for each drainage method in this study. For 90 mmh-1 and lower rainfall intensities, three drainage methods demonstrated similar drainage behaviors except for SD. The subsequent greater rainfall intensities were induced different maximum drain outflows for each drainage technique. The SWT was thought that it is the most drainable and applicable drainage technique in terms of hydrological perspectives. Therefore, for SWT, time-dependent water contents were also monitored using soil moisture sensors at different depths in the drainage layers. Soil water retention curve (SWRC) of each drainage layer obtained from calibration tests and empirical parameters were optimized with HYDRUS-3D model which solves 3-D Richards’s equation using finite element method through saturated unsaturated media by using water contents and suction pressure results. Observed drain outflow hydrographs were compared with simulated drain outflow hydrographs by using statistical indices of Nash-Sutcliffe Efficiency (NSE) index, Kling and Gupta Efficiency (KGE) index, and determination coefficient (R2). Experimental results and HYDRUS-3D simulations showed good compatibility with the values of NSE, KGE and R2 varied between 0.859-0.958, 0.594-0.972, and 0.868-0.975, respectively.