This paper presents new experimental data of the erosion rate and sediment transport rate during the processes of dam break caused by overtopping. In order to study the headcut migration, the erosion coefficient was calculated and its peak value was determined near the downstream edge of the dam crest. Then the characteristics of vertical erosion during dam break processes were analyzed by dividing the dam into three regions: the upstream region, middle region, and downstream region. The three regions show different features during headcut migration, but all are exposed to the most intense erosion at the third stage of the dam break process. Finally, three relevant parameters affecting sediment transport were discussed: the length of the dam crest, the inner slope, and the dam composition. The results show that a longer dam crest and flatter inner slope reduce the peak sediment transport rate and prolong the arrival time of peak sediment transport rate; and with the increase of the non-uniformity coefficient S, the peak sediment transport rate initially increases, and then decreases. This paper presents new experimental data of the erosion rate and sediment transport rate during the processes of dam break caused by overtopping. In order to study the headcut migration, the erosion coefficient was calculated and its peak value was determined near the downstream edge of the dam crest. Then the characteristics of vertical erosion during dam break processes were analyzed by dividing the dam into three regions: the upstream region, middle region, and downstream region. The three regions show different features during headcut migration, but all are exposed to the most intense erosion at the third stage of the dam break process. Finally, three relevant parameters affecting sediment transport were discussed: the length of the dam crest, the inner slope, and the dam composition. The results show that a longer dam crest and flatter inner slope reduce the peak sediment transport rate and prolong the arrival time of peak sediment transport rate; and with the increase of the non -uniformity coefficient S, the peak sediment transport rate initially increases, and then decreases.