A Method to Improve the Flood Maps Forecasted by On-Line Use of 1D Model

Pasquale G F Filianoti,Demetrio A Zema,Angelo Nicotra,Antonino Labate

doi:10.3390/w12061525

Abstract

Forecasting floods in urban areas during a heavy rainfall is the aim of every early warning system. 2D-models produce the most accurate flood maps, but they are practically useless as quasi real-time tools, because their run times are comparable to times of propagation of floods. Run times of 1D-model are of tens of seconds, but their predictions lack accuracy and many useful indicators of flood severity. Our aim is the identification of the 2D-model map that is more similar to the actual map, chosen among those simulated off-line. To this aim, we produce a rough flood map of the occurring event, through a quasi real-time simulation of the rainfall-runoff using a 1D-model. Then we apply an original method, named “ranking approach”, to perform the best matching. This method is applied to the Corace torrent (Calabria, Southern Italy), using 17 synthetic hyetographs to simulate the same number of rainfall-runoff events, using 1D (SWMM) and 2D (MIKE) models. The method proves to be effective in 65% of the cases, while in 82% of cases (i.e., for 14 cases out 17), the event produced by the same ietograph falls within the third rank.

Highlights

Flooding is one of the most frequent natural disasters [1]
If the hydraulic variables simulated by Storm Water Management Model (SWMM) are compared to the corresponding variables produced by MIKE models, differences of 7.1% and 32.7% were found for mean Vf and Q, respectively, while the differences in the mean T and Q0 were 13.6% and 25.5%
The differences in excess volumes and peak flows for the modelled rainfall-runoff events can be visually noticed from the V-Q plot, which shows how much each event simulated by SWMM is far from the corresponding event predicted by MIKE models (Figure 9)

Summary

Introduction

Flooding is one of the most frequent natural disasters [1]. The effects of flooding are severe in urban areas [2], where lost of life and heavy damage to infrastructures can be associated with the most hazardous flood events. The use of hydraulic and hydrological models provides system managers information about how the drainage system will respond to the most intense precipitations [7] and support planning and operation of early flood warning systems [8]. To this goal, many hydrologic computer models were developed to study watershed hydrology with applications in rural and urban areas [9,10].

Objectives

Results

Conclusion