###### Abstract
[PERSON] et al. [19] and [PERSON] et al. [20], respectively, applied the semi-distributed XAJ model in the upstream region of Lancang River and the Mishui basin, a tributary of the Xiangjiang River, in China. [PERSON] et al. [21] employed SWAT in the Mekong Basin region to explore hydrologic flows for water availability study. [PERSON] and [PERSON] [22] assessed the performance of the HBV model in hydrological simulations across the climatically and topographically diverse mainland of China. [PERSON] et al. [23] and [PERSON] et al. [24] explored hydrologic evaluations of GPM data using a VIC model in a tropical monsoon basin of Thailand and a humid basin of China, respectively. These studies collectively demonstrate the various applications of the daily IMERG precipitation data in hydrologic modeling. Similarly, hydrologic modeling applications have also been conducted for significant global river basins using the hourly products of IMERG precipitation for flood analysis: [PERSON] et al. [25] used a physically based distributed hydrologic model, GSSHA, to study a flood event in the city of Haftr Al Batin, Saudi Arabia. [PERSON] et al. [26] assessed the performance of IMERG in the RRI model for runoff simulation and flood inundation mapping for the Kelantan River basin, Malaysia. [PERSON] et al. [27] investigated the accuracy of flood discharge simulation with the BTOP model in the Fuji River basin, Japan. [PERSON] et al. [28] and [PERSON] and [PERSON] [29] adopted GR4H for evaluating the suitability of satellite precipitation for monitoring and forecasting floods in the Vilcanota River basin in the Cusco Region of Peru and the Andean-Amazon basins, respectively. [PERSON] et al. [30] and [PERSON] et al. [31] presented the comprehensive studies on the feasibility and hydrologic utility of GPM IMERG for flood simulations over the Chindwin River and Mishui basins in China using XAJ, respectively. [PERSON] and [PERSON] [32], [PERSON] et al. [33], [PERSON] et al. [34], [PERSON] et al. [35], [PERSON] et al. [36], [PERSON] et al. [37], and [PERSON] et al. [38] applied the HEC-HMS model to the river basins in Poland (Upper Skawa River), Morocco (Ghatt River and Tensift River), China (Xin'an River and Shouxi River), Malaysia (Langat River), and India (Upper Ganga River) for flood modeling, respectively. Nonetheless, these IMERG-used flood analyses lack sufficient evaluation of the modeling accuracy compared to traditional methods that rely on gauge observations or precipitation estimates from weather radars,such as those conducted by [PERSON] et al. [10] and [PERSON] [32]. Therefore, in order to expand the application of GPM precipitation data to ungauged watersheds, particularly in flood analysis, it is essential to conduct more comparative studies that assess the level of accuracy in the IMERG product-based flood simulation modeling by comparing it with those of well-established precipitation estimates (i.e., rain gauge observation and ground-borne radar precipitation). In South Korea, the availability of a robust in situ data infrastructure for rainfall observation, which includes numerous rain gauges and a ground-based radar system for precipitation estimation, provides significant advantages for evaluating the precision of GPM IMERG space-borne radar precipitation products [39; 40]. Moreover, South Korea's mountainous topography, covering approximately 65% of the land, introduces an additional dimension to the assessment; the spatial distribution of precipitation during rainfall storm events exhibits high variability, especially in dam watersheds that represent typical mountainous terrain. This intricate pattern of rainfall and the resulting changes in the runoff outflow show complicated characteristics, enabling a comprehensive evaluation that captures the influence of the unique characteristics (i.e., amount and spatial variability) from different types of precipitation products in flood simulation.