Hydrological models should be tested and evaluated for a wide variety of levels of urbanization before they are used to predict the impact of urbanization on catchment behavior. In this study, we illustrate a top–down approach of modifying step by step an hourly conceptual model structure (GR4H) to account for urbanization features. Modifying the original model structure included accounting explicitly for runoff from impervious surfaces by bypassing the soil moisture reservoir and varying the partitioning between quick flow and slow flow. These adaptations were chosen based on the reported specificities of urbanized catchments, namely, decreasing infiltration, increasing runoff, and fast runoff dynamics. Using a split-sample test, the relevance of each modification with regard to the reproduction of catchment response (i.e., observed streamflow) was assessed for a large sample of 273 urbanized catchments, located in France and the United States, for which mean total impervious area (TIA) varied between 0.05 and 0.59. Six continuous and three event-based criteria were used, and two statistical tests were applied to assess the significance of improvements. Results showed the following: (i) Tested modifications improved the ability of the model to reproduce the catchment response, especially high flows and observed streamflow amid dry conditions. (ii) Event-based evaluation using more than 45,000 events showed an improvement in predicting the event peak flow and event runoff volume, whereas no significant improvements were obtained in predicting the timing of peak flow. (iii) Newly added parameters were moderately to highly correlated with TIA, especially the calibrated proportion of impervious surfaces, which is promising as a hydrological validation of estimated urbanization measures from land cover. The tested modifications improved both the representation of urbanization processes and the reproduction of the observed streamflow, yielding a simple and credible model for predicting the impact of future urbanization scenarios on catchment response.

在将水文模型用于预测城市化对流域行为的影响之前，应对水文模型进行各种城市化水平的测试和评估。在这项研究中，我们说明了一种自上而下的方法，该方法逐步修改了每小时的概念模型结构（GR4H）以说明城市化特征。修改原始模型结构包括明确考虑不透水表面的径流，方法是绕过土壤水分库并改变快流与慢流之间的分配。根据报告的城市化集水区的特点，即减少的入渗，增加的径流和快速的径流动态来选择这些适应措施。使用分割样本测试，每个修改与集水区响应的再现相关性（即，在法国和美国，对273个城市化集水区的大量样本进行了评估（平均流量），其平均不透水面积（TIA）在0.05到0.59之间变化。使用了六个连续的和三个基于事件的标准，并且应用了两个统计测试来评估改进的重要性。结果表明：（i）经过测试的修改改进了模型再现流域响应的能力，尤其是在干燥条件下的高流量和观察到的水流。（ii）使用超过45,000个事件的基于事件的评估显示出在预测事件峰值流量和事件径流量方面的改进，而在预测峰值流量的时间方面没有获得显着改善。（iii）新添加的参数与TIA具有中等程度或高度相关性，尤其是不透水表面的校准比例，这有望通过土地覆被对估计的城市化措施进行水文验证。经过测试的修改既改善了城市化过程的表示形式，又改善了观测到的水流的再现，产生了一个简单而可靠的模型，用于预测未来城市化情景对集水区响应的影响。