本研究探討不同水流功率對於沖積扇開析型態之影響，實驗所使用的顆粒均為石英砂，透過調整水流量與扇面坡度來改變水流功率，實驗過程使用相機記錄影像並進行分析量化。水流由供水渠道輸送至堆積平台上預先堆好之乾砂沖積扇，待水流匯集形成渠道後，下切侵蝕扇面並將沖刷出的顆粒帶至扇端堆積成複成扇。在實驗過程中觀察到水流在匯集形成渠道前，因部分水流入滲至扇面土體導致扇面逕流變少而形成篩堆積，為觀察滲流對沖積扇開析過程的影響，因此另外以飽和的濕砂堆積沖積扇進行實驗。同時，也進行滲流實驗以討論扇面滲流破壞之位置。從實驗觀察中發現，水流功率與沖積扇的開析時間和開析速度呈高度正相關，且在濕砂堆積扇實驗中水流不會形成篩堆積。乾濕砂堆積扇之開析條件約為單位寬水流功率ω>1.5 kg?s^3 。水流量愈高則渠道的側向侵蝕能力愈大，而在渠寬較大的實驗中，渠道流更傾向於側向而非下切侵蝕。在流量較高的實驗中渠道在實驗過程中皆保持一定的側向侵蝕能力，而下切侵蝕則在實驗初期較大，隨著實驗時間逐漸趨緩。B?y_c 為一定值且幾乎不受單位寬水流功率所影響，渠道的下切與側向侵蝕能力成反比。;This study describes and discusses the influence of different stream powers on the dissection of alluvial fans. The particles used in the experiment are all silica sand. Adjusting the water discharge and the slope of the fan to control stream power. A camera is used to record images during the whole experiment. Water is supplied from a channel to an alluvial fan on the platform. After the flow forms a channel, the fan surface is incised by the channel and lead to dissection. The flow brings the eroded particles from the fan surface to fan toe and forms a new composite fan. During the experiment, it was observed that before the forming of a channel, the runoff is reduced due to infiltration at the fan surface and sieve lobes occur. We also did experiments to observe the influence of seepage on the fan. We found stream power is correlated with the progress of alluvial fans dissection. The opening conditions of the dry and wet alluvial fans are about unit width stream power ω>1.5 kg?s^3 . B?y_c have a certain value under any unit width stream power, and the ability of channel incision is inversely proportional to channel lateral erosion.
