Rainfall-runoff models require an extensive set of input data such as the watershed boundary, topographic elevations, surface roughness, and precipitation rates. With the inclusion of infiltration effects, additional input parameters such as the hydraulic conductivity of the underlying soil, the capillary pressure head at the wetting front, moisture deficit, and total infiltration depth are also required. Furthermore, when multidimensional (1D/2D) hydrodynamic models, which are developed to reduce computational cost for study areas with small-scale channels, are used, an additional dataset describing the network of channels is also required. The acquisition and incorporation of this input data into models is often performed on a site-by-site basis using ad hoc procedures and methods. In this study, a general methodology to obtain the required inputs from a small number of datasets that are publicly available and that have wide availability within the US is proposed. Specifically, watershed boundaries and channel networks are extracted from the 3D Elevation Program (3DEP) provided by the United States Geological Survey (USGS), which also provides the elevation data. Surface roughness coefficients are determined with National Land Cover Database, and the input parameters required for modeling infiltration are obtained from the Soil Survey Geographic Database (SSURGO) provided by the United States Department of Agriculture (USDA). Other datasets including channel cross-section profiles and precipitation rates are obtained from locally available datasets such as field survey and gauges. Having acquired the relevant data, this study also investigates how this data of varying spatial and temporal resolution can be accurately and effectively integrated into the unstructured mesh modeling framework that has been developed — specifically, a multidimensional discontinuous Galerkin (DG) finite element model, which solves 1D and 2D kinematic wave equations for channel and overland flow, respectively. As a case study, the developed input data methodology and modeling framework is applied on the Walnut Gulch Experimental Watershed (WGEW), located in southeastern Arizona.