Model Type: Rainfall-Runoff Model
Model Name: PMF Analysis Module
Introduction
Dam safety assessments are usually conducted regularly to investigate the risks associated with the dam and propose remedies to ensure effective reservoir operations. One crucial aspect of the evaluation involves performing hydrological analyses to determine if the existing spillway can successfully handle the probable maximum flood (PMF) downstream. An open-source geographic information system (open-source GIS) was adopted in this project to build the information platform and integrate the PMF Analysis Module in the 2-year (2019-2020) project.
Considering that during typhoon and flood periods, a large amount of floodwater will be introduced into the reservoir from the upstream watershed, the design of the spillway must be based on the principle of accommodating the probable maximum flood. Therefore, the hydrological design process needs to estimate the probable maximum precipitation (PMP) for the reservoir watershed and then use a design storm and rainfall-runoff models to estimate the probable maximum flood (PMF). The PMF analysis flowchart is shown in Figure 1.
This model is developed using an open-source Geographic Information System (open-source GIS) framework, which involves analysis models, spatial layers, and establishing a framework for probable maximum flood analysis. The Probable Maximum Flood Analysis Module includes three PMP analysis methods: the storm transposition method, the World Meteorological Organization (WMO) methods, and the Typhoon Rainstorm Model. After calculating the probable maximum precipitation, users can set parameters for the kinematic-wave-based geomorphologic IUH (KW-GIUH) or the dimensionless unit hydrograph (IUH) model to estimate the probable maximum flood (as shown in Figure 2). This module integrates PMP and PMF calculation functions, providing a convenient way for engineers to obtain most of the required information for safety assessment analysis work.
Figure 1. The PMF analysis flowchart
Figure 2. Probable Maximum Flood Analysis Module