Effects of urban drainage inlet layout on surface flood dynamics and discharge

Abstract

<p>Drainage inlets, the primary conduits for surface floodwater into underground facilities, significantly influence the performance of a drainage system. This study employs a two-dimensional hydrodynamic model to investigate how drainage inlet distribution affects urban flood dynamics and drainage flow discharge. We first validate the model with dataset obtained in a dedicated experiment observing urban surface and drainage flows. We identified two common layouts of drainage inlets, namely straight-line distribution (SLD) and surround type distribution (STD), and based on the two layouts, we simulated detailed surface flood dynamics and drainage discharge under various urban flood conditions and inlet spacing scenarios. The results indicate that SLD exhibits higher drainage capacity in shorter time and greater total drainage volume under urban peripheral flood condition, while STD consistently outperforms in draining urban surface flooding induced by intense rainfall. It is also found that inlet spacing plays a crucial role in affecting drainage efficiency. To be specific, both layouts with medium spacing (<em>l</em>₀ = 0.53 for SLD and 0.93 for STD) near flood-prone areas perform better when a sudden-onset peripheral flooding occurred; however, in the case of rainfall-induced flooding, maximizing inlet spacing and strategically distributing them across urban streets proves to be a more effective strategy for draining floodwater. Individual inlets near the ends of SLD and inlets at far-corners of STD shoulder higher drainage loads. This study provides valuable insights for optimizing inlet layout strategies under various urban flood conditions and improving floodwater collection.</p>