Monday, April 29, 2024

ICM InfoWorks Hydrology Rules

InfoWorks ICM (Integrated Catchment Modelling) is a powerful and comprehensive modeling software that enables users to simulate rainfall-runoff processes using two main methods: traditional subcatchment hydrology and Rain-on-Grid on 2D zones. This article delves into the traditional subcatchment hydrology approach, which is comparable to other node-link hydrologic and hydraulic (H&H) modeling tools.

In the traditional subcatchment hydrology method, users are required to delineate subcatchments (also referred to as subbasins or drainage areas) and define the runoff flows that are routed to subcatchment outlets (nodes, links, or others) after accounting for various losses. InfoWorks ICM offers a wide range of common methods for modeling evaporation, initial loss, runoff volume, and routing, as summarized in Table 1.

To set up the subcatchment hydrology, users need to input the required parameters in the subcatchment, land use, and runoff surface property editors or the subcatchment grid windows within InfoWorks (Figures 1 and 2). These editors allow users to define the characteristics of the subcatchments, such as area, slope, and infiltration parameters, which are essential for accurate rainfall-runoff modeling.

However, special attention should be given to the rainfall event editor, where hyetographs and initial condition data can be entered (Figure 3). InfoWorks provides multiple locations for entering initial condition data, which can lead to confusion and inconsistencies in the model setup. To avoid this, it is highly recommended that initial condition data be provided solely in the subcatchment runoff surface property editor, unless the rainfall event editor is the only place for a specific initial condition parameter.

When running the model, it is crucial to ensure that the subcatchment rainfall profile name (e.g., "1" in Figure 4) matches the exact name of the rainfall profile in the rainfall event editor (Figure 5). If no matching profile is found, the model will default to using the leftmost rainfall profile in the editor table. This can lead to unintended results if the profile names are not properly matched.

In addition to the traditional subcatchment hydrology method, InfoWorks ICM also offers the Rain-on-Grid on 2D zones approach, which will be covered in a separate article. This method allows for a more detailed representation of the rainfall-runoff process by directly applying rainfall to the 2D surface mesh, eliminating the need for subcatchment delineation.

In conclusion, the traditional subcatchment hydrology method in InfoWorks ICM provides a robust way to model rainfall-runoff processes, offering a variety of methods for evaporation, initial loss, runoff volume, and routing. However, users should pay close attention to the input of parameters, especially in the rainfall event editor, to ensure accurate and consistent results. By following best practices and understanding the intricacies of the software, users can effectively utilize InfoWorks ICM to simulate complex hydrologic and hydraulic systems.

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