Assessing the Performance of Different Time of Concentration Equations in Urban Ungauged Watersheds: Case Study of Cartagena de Indias, Colombia

• Published in: Hydrology 2020-09, Vol.7 (3), p.47
• Main Authors: González-Álvarez, Álvaro, Molina-Pérez, José, Meza-Zúñiga, Brandon, Viloria-Marimón, Orlando M., Tesfagiorgis, Kibrewossen, Mouthón-Bello, Javier A.
• Format: Article
• Language: English
• Subjects: Best management practices; Cartagena de Indias; Channel flow; Concentration time; Drainage systems; Environmental risk; Flood management; Gauges; Hydraulic structures; Hydrological analysis; Hydrology; Mathematical analysis; Natural resources; non-stationarity; Overland flow; Performance assessment; Resource conservation; Restoration; Risk analysis; Runoff; Runoff volume; Stormwater; Stormwater management; Studies; Surface runoff; Systems design; time of concentration; Time series; ungauged urban watershed; Urban planning; Variables; Velocity; Water management; Watershed management; Watersheds
• ISSN: 2306-5338; 2306-5338
• DOI: 10.3390/hydrology7030047

In ungauged watersheds, the estimation of the time of concentration (Tc) is always a challenging task due to the intrinsic uncertainty involved when making assumptions. Given that Tc is one of the main inputs in a hydrological analysis for the design of hydraulic structures for stormwater management, ten equations (including one proposed in several local studies) and two Tc methodologies (overland flow time plus channel flow time) were used to compute the Tc in fifteen urban ungauged watersheds, located in Cartagena de Indias (Colombia), with different area sizes and slopes to statistically assess their performance against the value obtained via the Natural Resources Conservation Service (NRCS) velocity method (assumed to be the true value). According to the Nash–Sutcliffe efficiency index, none of the equations proved to be reliable in all watersheds as only four equations predicted the Tc value in 53% of the cases. In addition, based on the percent bias, all equations tended to significantly over- or underestimate the Tc, which affects the quantification of the runoff volume necessary for, among others, the implementation of best management practices for watershed management (e.g., conventional and/or sustainable drainage system design), flood-prone area delineation and flood risk analyses, urban planning, and stream restoration.