Two-dimensional tank experiments were conducted to establish a method for assessing the stability of a sand-pack structure on a beach. The results of 89 experimental cases showed that piping out of nourished sand and pulling out of a sand-pack on a slope were typical collapsing processes, and these were caused by the return flow of a wave over topping. Lifting up of the seaward tip of the sand-pack by wave run-up was also observed. The desirable weight of a sand-pack for avoiding these pulling out and lifting up behaviors was investigated. Based on these findings, structures for moderating sand dune erosion were designed, and a field experiment was conducted. Through the one-year-long field experiment, the developed structures were confirmed to endure against even high typhoon-induced waves.