The spatial distribution of the strength inside river dikes is generally identified through sounding tests. In this research, the electric cone penetration test (CPT) is employed, and spatially long- A nd short-interval tests are mixed to efficiently evaluate the piping risk to a dike. The indicator simulation (IS) method is used as the geostatistical method to simulate the N value distribution and to predict the weak area inside the dike. The synthesized approach of the CPT and the surface wave method (SWM), which is one of the geophysical methods, is proposed to compensate for the shortcoming of each approach when conducting the IS. Consequently, the correlation structure inside the dike can be identified accurately, the high resolution of the spatial distribution of the N values can be visualized, and the piping risk to the dike can be discussed based on the results of the investigation.