Spatial variations of sediment movement initiation in the Chungliao creek at Liukuei experimental forest of southern Taiwan

In this study, peak flows of different recurrence years at Chungliao creek within Liukuei experimental forest of southern Taiwan were deterimined with rainfall depth-duration-frequency and design hyetograph estimated equations as well as SCS curne number storm flow model. Spatial variation of sediment movement initiation for eight cross sections of the Chungliao creek was estimated with four kinds of current incipient motion methods. Based on the fixed cross sections of the Chungliao creek, the differences of estimated particle sizes among Shields, Mavis & Laushey, Neill and Yang methods were only from -16.5% to 26.5%. Differences of estimated particle sizes for spatial variation of eight cross sections by Shields, Mavis & Laushey, Neill and Yang methods were very large and about from five to seven times. Spatial variations of sediment incipient motion in the Chungliao creek were affected by slopes and water depths of cross sections. particle sizes of incipient motions at different cross sections increased as slopes and water depths increased.
Peak flows of 1, 2.33, 5, 10, 20, 25, 50, 100 year return periods were 41.4 cms, 49.5 cms, 60.1 cms, 70.1 cms, 81.4 cms, 85.4 cms, 98.8 cms, 114.0 cms. Spatial variation ranges of particle sizes for incipient motion of sediments being averged by Shields, Mavis & Laushey, Neill and Yang methods were 17.3-93.9 cm, 19.5-103.0 cm, 22.2-114.0 cm, 24.5-123.4 cm, 27.1-133.4 cm, 28.0-136.8 cm, 30.8-147.6 cm, 33.9-159.0 cm for eight cross sections of the Chunglioa creek.