Abstract

The establishment of reliable water level prediction models is vital for urban flood control and planning. In this paper, we develop hybrid models (GA-XGBoost and DE-XGBoost) that couple two evolutionary models, a genetic algorithm (GA) and a differential evolution (DE) algorithm, with the extreme gradient boosting (XGBoost) model for hourly water level prediction. The Jungrang urban basin located on the Han River, South Korea, was selected as a case study for the proposed models. Hourly rainfall and water level data were collected between 2003 and 2020 to construct and evaluate the performance of the selected models. To compare the prediction efficiency, two other tree-based models were chosen: classification and registration tree (CART) and random forest (RF) models. A comparison of the results showed that two hybrid models, GA-XGBoost and DE-XGBoost, outperformed RF and CART in the multistep-ahead prediction of water level, and the relative errors of the hybrid model ranged from [2.18%-9.21%], compared to [3.76%-10.41%] and [2.99%-11.88%] for the RF and CART, respectively. Reliable performance was also supported by other measures. In general, the GA-XGBoost and DE-XGBoost models displayed relatively similar performance despite their small differences. The CART model was not preferable for multistep-ahead water level predictions, even though it yielded the lowest Akaike information criterion (AIC) value. This study verifies that despite having some drawbacks when considering long step-ahead prediction and model complexity, hybrid XGBoost models might be superior to many existing models for hourly water level prediction.

Highlights

  • Floods are among the greatest risks in most cities around the world

  • We developed and examined four tree-based models: GAXGBoost, differential evolution (DE)-XGBoost, random forest (RF), and classification and registration tree (CART) models

  • Through a case study in the Jungrang urban basin, South Korea, the performance of the four tree-based models was compared based on multistep-ahead predictions of water levels

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Summary

Introduction

Floods are among the greatest risks in most cities around the world. Due to hydrometeorological and hydrological variability induced by climate change, urban floods are more complex than in previous decades [1], [2]. Various approaches have been established and applied. These attempts can be divided into two groups. The first group involves the coupling of hydrological and meteorological forecasting models for predictions based on physical rainfall-runoff formulations [4]– [6]. These methods generally use simplified assumptions for hydrological processes and require forecasted hydrometeorological data. The second group includes datadriven methods, such as statistical approaches and machine learning approaches, that do not require excessive data for hydrological processes and are not difficult to apply. Datadriven methods mainly use the relevant features of past data to make hydrological predictions

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