Quality of Local Drainage Systems in Underserved Communities: Assessment Method and Tool using Lidar Data

Abstract

A properly functioning local stormwater drainage system is essential for mitigating flood economic, health, and safety risks. Failure of a local drainage system occurs when runoff overloads the system and flows into the streets and surrounding low-lying areas. The impacts of these failures include flooding and standing water, which lead to property damage, health risks (e.g., mold, mosquitoes), and pollution (e.g., pesticides, heavy metals carried by the runoff). Local drainage systems are designed to collect and convey stormwater runoff through multiple infrastructure components (such as roadside ditches, drain inlets, pipes, ponds). This study provides a method for evaluating roadside drainage channels using field measurements obtained from mobile lidar (Light Detection and Ranging) scanning systems. We applied this method to evaluate the quality of roadside drainage channels in three underserved communities in Texas. The three communities are the Sunnyside neighborhood in Houston (Harris County), neighborhoods in the City of Rockport (Aransas County), and the Hoehn colonia (Hidalgo County). These communities were selected because they have a history of localized flooding and rely on roadside ditches as their principal infrastructure for runoff control. Ditch conditions were evaluated based on five channel geometric properties (bottom width, channel depth, front slope, back slope, longitudinal slope), the channel’s hydraulic capacity, and the channel’s level of service (LOS). The ditch properties and the LOS are visualized in a geographic information system (GIS). Finally, the ditch properties and LOS were compared across the three communities to determine prevailing failure types.