Browsing by Author "Acevedo González, Ihan-Jarek"
  • Publication
    Hydrograph Separation Method (HSM) for the design of storm drain inlets
    ( 2022-07-08) Acevedo González, Ihan-Jarek ; Silva Araya, Walter ; College of Engineering ; Rodríguez Román, Daniel ; Pagán Trinidad, Ismael ; Department of Civil Engineering ; Méndez, Nancy
    Urban stormwater drainage systems are part of the urban drainage infrastructure. They encompass the transportation system, structural surroundings, and the topography of the adjacent environment. Adequate stormwater drainage design prevents flooding hazards and protects life and properties. This research proposes a methodology to improve stormwater drainage design named the Hydrograph Separation Method (HSM). The Hydraulic Engineering Circular No. 22 drainage manual (FHWA, 2013) defines storm drain inlet efficiency through a series of semi-theoretical equations. Efficiency is the effectiveness of an inlet to collect the discharge along a street gutter as compared with the total discharge flowing on the street. This project used those relations and developed an algorithm that takes the street runoff hydrograph and separates it into intercepted flow by the inlet, and carryover flow bypassing the inlet and continuing along the roadway. The software is written in MS Excel Visual Basic for Applications (VBA). It facilitates the design process of street drainage systems and allows the analysis of different alternatives and how they impact the system’s performance. A sensitivity analysis provided additional information regarding individual parameter impact on overall inlet efficiency and flood levels, concluding that longitudinal slopes and cross slopes have the least and most effect, respectively, on horizontal flow spread and inlet efficiency. It also showed that grate width has a greater impact on grate interception efficiency than grate length, suggesting a correct orientation when installing them. Stormwater levels on the streets will be estimated with higher precision and, the minor system design will be improved by having better estimates of inlet discharges. Results from the HSM are incorporated in stormwater simulation programs, such as EPA SWMM, for better design of the minor and major drainage systems. Design of low-impact development (LID) measures will benefit from the HSM by having better estimates of flows into areas with vegetation or infiltration sites.