Effects of Granular Material Deposition on the Road’s Stormwater Drainage System

Travel safety and comfort depend on the design and maintenance of road and stormwater drainage systems. In low-lying areas, poor drainage systems can—especially near underpasses—lead to flooding and serious risks, such as reduced load-bearing capacity hydroplaning, where tires lose grip. This study focuses on the effect of granular material deposits on the surface roughness of roadside gutters, as expressed through the Gauckler– Strickler coefficient. The literature equations have pointed out that this coefficient is largely affected by the grain size distribution of granular material. To this end, a field study was carried out in six urban roads in San Nicola la Strada, Italy, with the objectives of the following: (1) identifying the grain size distribution of the material deposited in roadside gutters; (2) estimating how such material decreased in the cross-sectional area of the gutters, as well as increasing their flow resistance, ultimately resulting in decreased water conveyance. Considering gutters with deposited material rather than clean ones results in the failure of three out of six gutters to effectively drain stormwater.