**3. Field observation at Kimigahama Beach**

#### **3.1 Method**

First, the shoreline changes on Kimigahama Beach were investigated using the aerial photographs taken in 1963 and 2018, as shown in **Figure 4**. The shoreline changes before and after the construction of the artificial reef can be clarified using these aerial photographs. The longitudinal profiles along transect Nos. 1–5 shown in **Figure 4** were measured using an RTK-GNSS on 9 July 2019. Of the survey lines,

*Numerical Simulation on Sand Accumulation behind Artificial Reefs and Enhancement… DOI: http://dx.doi.org/10.5772/intechopen.107014*

transect Nos. 2 and 4 were aligned across the salient formed after the construction of the artificial reef, and transect Nos. 1, 3, and 5 were aligned on both sides of the salient. Then, the beach topography along each transect was compared. The conditions of the coast were also observed on 14 June 2022 and foreshore and backshore materials were sampled along transect No. 4. Furthermore, beach topography around the artificial reefs was investigated in detail using a bathymetric survey map prepared in 2002 by the Chiba Prefectural Government.
