Assessing the Uncertainty Associated with Flood Features due to Variability of Rainfall and Hydrological Parameters

Abstract

An assessment of uncertainty in flood hydrograph features, e.g., peak discharge and flood volume due to variability in the rainfall-runoff model (HEC-HMS) parameters and rainfall characteristics, e.g., depth and duration, is conducted. Flood hydrographs are generated using a rain pattern generator (RPG) and HEC-HMS models through Monte Carlo simulation considering uncertainty in stochastic variables. The uncertainties in HEC-HMS parameters (e.g., loss, base flow, and unit hydrograph) are estimated using their probability distribution functions. The flood events are obtained by simulating runoff for rainfall events using the generated model parameters. The uncertainties due to rainfall and model parameters on generated flood hydrographs are evaluated using the relative coefficient of variation (RCV). The results reveal a higher RCV index for flood volume (RCV = 153) than peak discharge (RCV = 116) for a 12-hr rainfall duration. The average relative RCV (ARRCV) index computed for hydrological component (e.g., base flow, loss, or unit hydrograph) indicates the highest impact of rainfall depth on flood volume and peak. The results indicate that rainfall depth is the main source of uncertainty of flood peak and volume.

Alteration of the Fogera Plain flood regime due to Ribb Dam construction, Upper Blue Nile Basin, Ethiopia

“…However, slight over and under predictions of the low and high flows were observed (Figures 5 and 6), which is a common problem for hydrological models (Zhang and Savenije 2005). Moreover, the results of hydrological modeling may have uncertainties related to model input data, modeling parameters and model selection (Sharafati et al 2020). River discharge computation based on staff gauge height reading is another source of uncertainty as the rating curves may not be updated regularly for the alluvial river section, which is affected by the river bank and bed morphological adjustments.…”

Downstream Consequences of Ribb River Damming, Lake Tana Basin, Ethiopia

“…However, a slight over and under prediction of the low and high flows were observed (Figure 5.3 and Figure 5.4), which is a common problem for hydrological models (Zhang and Savenije, 2005). Moreover, the results of hydrological modeling may have uncertainties related to model input data, model parameters and, model selection (Sharafati et al, 2020). River discharge computation based on staff gauge height reading is another source of uncertainty as the rating curves may not be updated regularly for the alluvial river section, which is affected by the river bank and bed morphological adjustments.…”

Evaluation of Future Streamflow in the Upper Part of the Nilwala River Basin (Sri Lanka) under Climate Change

“…Direct runoff and baseflow are two distinct components in a hydrograph. Among the five baseflow methods available in HEC-HMS [61], baseflow for the UNRB was determined by the exponential recession method due to several reasons including due to capability of simulating continuous streamflow, less number of parameters, and the compatibility with the selected loss model. All the routing methods included in the HEC-HMS calculate a hydrograph downstream, given an upstream hydrograph as a boundary condition by solving the continuity and momentum equations.…”