臺灣地區地形東西短南北長,地勢高峻狹長,使得降雨時空分佈不均,常受颱風豪雨及極端降雨影響,引發臺東地區上游集水區多處崩塌,大量土砂傾洩而下,淤積於中、下游河道中,通洪斷面減少,工程構造物也遭受到損毀或埋沒,危及下游居民及道路等保護對象之安全。 研究結果顯示:土壤沖蝕部分,通用土壤流失公式(Universal Soil Loss Equation; USLE)為常用之土壤沖蝕量估算模式,用於估算臺灣地區之各土壤沖蝕因子,常有高估之現象,本研究使用陳樹群等人(1998)針對臺灣地區特有條件,建立土壤沖蝕指標模式(Soil Erosion Index Model; SEIM)與通用土壤流失公式,對於計算結果進行比較,指標法在本研究中,顯示其對特殊降雨事件歷經之年,所造成土壤沖蝕之敏感度高於USLE,此兩種計算結果趨勢一致;土砂部分,2009 年莫拉克颱風挾帶的超大豪雨是安朔溪土砂產量最主要之因素,目前臺灣對於集水區治理之成效,並無明確的評估方式,因此本研究利用土壤指標模式,配合集水區之特性,推估出安朔集水區之合理泥砂排放量由33.6#westeur024#104m3降為26.2#westeur024#104m3,顯示安朔集水區從莫拉克逢颱風後河道清疏工程治理至今,因歷年之施作工程不同而有所差異,本研究希冀藉此成果來評估集水區清疏工程對河道整治的功效,以提供集水區土砂治理規劃時之參考依據。
The topography of hillslopes located at Taitung County is quite steep with fragile geological structure have led to the uneven temporal-spatial rainfall distribution, lead to a large amount of landslides occurred on many rivers upper stream watershed in Taitung, the large volume of sediment from landslides to block rivers and let it bed obstruct high, lead to downstream residents and roads faced with the potential threat of secondary disasters. The results show USLE is the common one of estimating soil erosion, this result is consistent trend of two calculations in Taiwan, the results show higher estimating values. Take Chen et al.(1998) set up SEIM(Soil Erosion Index Model), the model developed and USLE to compare shows the tendency is similar, However, SEIM with rainfall showed the high sensitivity of soil erosion . that Ansowshi was affected by super Typhoon Morakot (2009) dumped heavy rains, the main factors of sediment yield in Ansowshi. However evaluation model based on the complete ratio have yet to in Taiwan. So the soil erosion index and the qualities of watershed characteristics can be used to simulate the sediment yield. Take Ansowshi watershed for example, the natural sediment yield are about 33.6#westeur024#104m3/year reduced to 26.2#westeur024#104m3/year, sediment dredging management since Typhoon Morakot to 2014 remediation to good effect in Ansowshi watershed. The related research could be provided reasonable the watershed management in the future.