Event selection and two-stage approach for calibrating models of green urban drainage systems

Abstract

Abstract. The calibration of urban drainage models is typically performed based on a limited number of observed rainfall–runoff events, which may be selected from a larger dataset in different ways. In this study, 14 single- and two-stage strategies for selecting the calibration events were tested in calibration of a high- and low-resolution Storm Water Management Model (SWMM) of a predominantly green urban area. The two-stage strategies used events with runoff only from impervious areas to calibrate the associated parameters, prior to using larger events to calibrate the parameters relating to green areas. Even though all 14 strategies resulted in successful model calibration (Nash–Sutcliffe efficiency; NSE >0.5), the difference between the best and worst strategies reached 0.2 in the NSE, and the calibrated parameter values notably varied. The various calibration strategies satisfactorily predicted 7 to 13 out of 19 validation events. The two-stage strategies reproduced more validation events poorly (NSE <0) than the single-stage strategies, but they also reproduced more events well (NSE >0.5) and performed better than the single-stage strategies in terms of total runoff volume and peak flow rates, particularly when using a low spatial model resolution. The results show that various strategies for selecting calibration events may lead in some cases to different results in the validation phase and that calibrating impervious and green-area parameters in two separate steps in two-stage strategies may increase the effectiveness of model calibration and validation by reducing the computational demand in the calibration phase and improving model performance in the validation phase.

Reducing uncertainties in urban drainage models by explicitly accounting for timing errors in objective functions

“…37%. 1-minute observations of rainfall and catchment outflow were available (with only limited gaps) for the snow-free periods from June 2016 to November 2019; details on the measurement campaign are available in earlier works (Broekhuizen 2019;Broekhuizen et al 2020). Uncertainties in the flow measurements were estimated by applying the results of laboratory benchmarks for the level and velocity (Aguilar, McDonald, and Dymond 2016) to the circular pipe using the law of propagation of uncertainties (e.g.…”

“…A previously developed finely discretized SWMM model (Broekhuizen et al 2020) was used, where each of the 146 subcatchments was completely impervious or completely pervious and physical subcatchment properties such as width and slope could be estimated directly (see e.g. Krebs et al 2014;Petrucci and Bonhomme 2014) .…”

“…The calibration parameters are listed in Table 1. The number of calibration parameters was lowered compared to Broekhuizen et al (2020), since the focus of the current study was on the comparison of different approaches to model evaluation, rather than detailed finetuning to maximize model performance. A multiplier for the rainfall input is applied to allow adjusting runoff volume.…”

An Investigation of Modelling Accuracy Needs for Urban Design Flood Estimation

“…After considering these alternatives, the SWMM system ( [18]) was used herein for data generation. This model has received extensive application; see, for example, [19] and [20] for recent applications.…”

Real-time foul sewer hydraulic modelling driven by water consumption data from water distribution systems

“…To deal with this problem, a widely used approach is to calibrate a model to estimate manhole inflows with the aid of limited in-sewer observations (Korving and Clemens, 2005). While some calibration methods are available in the literature (e.g., di Pierro et al, 2005, Khu et al, 2006, Broekhuizen et al, 2020, they mainly focus on calibrating the underlying rainfall-runoff relationship for the combined sewer systems in an off-line manner, thereby predicting the floods or sewer overflows caused by rainfall. These previously published methods, therefore, cannot be used or at least are difficult to estimate FSS manhole inflows in real-time.…”