Abstract
The application of hydrologic and hydrodynamic models in flash flood hazard assessment is mainly limited by the availability of robust monitoring systems and long-term hydro-meteorological observations. Nevertheless, several studies have demonstrated that coupled modeling approaches based on event sampling (short-term observations) may cope with the lack of observed input data. This study evaluated the use of storm events and flood-survey reports to develop and validate a modeling framework for flash flood hazard assessment in data-scarce watersheds. Specifically, we coupled the hydrologic modeling system (HEC-HMS) and the Nays2Dflood hydrodynamic solver to simulate the system response to several storm events including one, equivalent in magnitude to a 500-year event, that flooded the City of Tena (Ecuador) on 2 September, 2017. Results from the coupled approach showed satisfactory model performance in simulating streamflow and water depths (0.40 ≤ Nash-Sutcliffe coefficient ≤ 0.95; −3.67% ≤ Percent Bias ≤ 23.4%) in six of the eight evaluated events, and a good agreement between simulated and surveyed flooded areas (Fit Index = 0.8) after the 500-year storm. The proposed methodology can be used by modelers and decision-makers for flood impact assessment in data-scarce watersheds and as a starting point for the establishment of flood forecasting systems to lessen the impacts of flood events at the local scale.
Highlights
The assessment of natural hazards, such as flash floods, remains a challenging issue in environmental sciences [1]
Since high performance metrics are difficult to achieve using a one-minute time step, and the Moriasi et al [21] performance ratings are for monthly time-step evaluations, we considered that our model had an acceptable performance in simulating event E5, which obtained a Nash-Sutcliffe efficiency coefficient (NSE) of 0.42 and a Percent Bias (PBIAS) of 23.44% (Figure 4)
This study coupled HEC-HMS and Nays2Dflood with event sampling and survey data to simulate the hydrologic response of data-scarce watersheds for a flood hazard assessment in the city of Tena
Summary
The assessment of natural hazards, such as flash floods, remains a challenging issue in environmental sciences [1]. Flash floods caused by extreme rainfall events associated with climate change have increased in the past few years [2,3,4]. The development and implementation of measures that diminish flash flood impacts and safeguard people and civil infrastructure are imperative. In this context, numerical models have been found to be reliable tools for flash flood hazard assessment. Hydrological and hydrodynamic models have been widely applied to describe flash flood dynamics at the watershed scale and project potential impacts on urban areas.
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