In small-scale measurements, a ground-penetrating radar (GPR) is often used with a higher frequency to detect a small object or changes in the ground. GPR becomes more sensitive to the heterogeneity of soil when a higher frequency is used. Soil heterogeneity scatters electromagnetic waves and the scattered waves are observed as unwanted reflections that are often referred to as clutter. Data containing high amplitude clutter are difficult to analyze and interpret because clutter disturbs reflections from objects to be detected. Therefore, modeling GPR clutter is useful to assess the effectiveness of GPR measurements. The authors have developed and demonstrated such a technique with data acquired during an infiltration experiment. In this study, the technique was applied to GPR and time domain reflectometry (TDR) data repeatedly acquired on an outdoor test site for a few months. The modeling results using the TDR data are similar to the clutter power directly extracted from the GPR data. Therefore, the technique works although it requires some modifications for more accurate modeling.