The Lam Phra Phloeng dam was constructed in 1963 and is located in the Nakhon Ratchasima province. The dam has severely reduced water level caused by deforestation and agriculture at the upper land. Sediment cores were collected using a gravity corer. The 210 Pb activities were measured using alpha and gamma spectrometry and sedimentation rates were determined. The sedimentation rates decreased gradually from the upstream to the crest of the dam. The high sedimentation rate may be due to the inflow from the tributary as well as eroded materials that come from the upland area to the dam.