沉積物通量反應了構造抬升、氣候事件與地表作用的綜合作用，然而在陡峭且受颱風影響的集水區中，十年尺度的侵蝕分布始終難以解析。位於集水區出口的水文測站量測雖能掌握集水區整體的產砂量，卻無法揭示沉積物在流域內部的產生、儲存與傳輸的空間分布。而作為替代方案的 DEM（數值高程模型）差分法，則長期受限於兩項問題而難以使用：一是基於穩定地表的對齊方法難以適用在穩定地面稀少的區域；其二是DEM資料本身帶有植被冠層偏差與感測器導致之偽影等雜訊，其量值往往超過地形差分訊號。 本論文發展並應用一套同時克服上述兩項限制的DEM差分法，並以其量化構造與地表作用活躍的臺灣南部中央山脈荖濃溪流域（約1，373平方公里）與其一支流之濁口溪流域（約375平方公里）的十年尺度地表侵蝕作用與沉積物再分布。第一項研究提出一種基於傅立葉頻譜分析的DEM的垂直對齊方法，可在不依賴大量穩定地表的情況下辨識並移除多期DEM之間的垂直偏差。本研究以濁口溪為例，使用1990至2020年間的開源全球與區域DEM進行高程對齊與DEM差分分析。校正後的高程差分結果顯示：三十年期間的平均侵蝕速率為每年14.19毫米，最近十年（2011年至2020年）則為每年10.46毫米。近十年侵蝕速率的下降反映了極端降雨事件的明顯減少，與下游水文測站獨立推估之懸浮載結果一致。本研究顯示使用本研究發展的對齊方式可顯著降低對齊造成的垂直誤差，使侵蝕訊號變得有代表性，讓過去未被充分利用的歷史與衛星DEM提供可靠的十年尺度沉積物收支分析。 第二項研究將前述架構延伸至荖濃溪流域，用以分析2000至2020年流域內的侵蝕與沈積物再分布，期間包含臺灣有紀錄以來降雨量最高的颱風：2009年的莫拉克颱風。研究首先以本地的空載光達的DEM為基準將多組全球DEM進行比對。分析結果指出，由於NASADEM具有低頻譜雜訊、極少的空值填補以及一致的觀測時間，使其為適用的歷史DEM。為了消除的植被冠層偏差以獲得更低的體積不確定性（雜訊），本研究先以全球冠層高度模型校正局部超過30公尺植被訊號，再施以頻譜垂直基準校正。經過植被偏差移除處理後，體積不確定性由約187百萬立方公尺降至約44百萬立方公尺。經過DEM差分計算後各子集水區的侵蝕速率平均約為每年15.3毫米，在受崩塌影響的支流中可達約每年551毫米。然而，侵蝕產生的物質中有87.6% 仍儲存於流域之內，主要以谷底充填沉積、沖積扇及主河道淤積的形式存在。由此得到的全流域淨剝蝕速率為每年5.06 ± 1.60毫米。儘管期間發生多次極端事件，此值仍與長期（10³ 至10⁶年）由宇宙射線生成核種與熱年代學推估的侵蝕、剝蝕速率（約每年 3至6毫米）高度一致。本研究所觀察到的沉積物緩衝現象即是在十年尺度上將局部極端侵蝕加以空間平均的結果。 綜合前述兩項研究顯示，重複觀測的地形資料經過適當校正植被高度與垂直偏差，即可同時解析十年尺度的侵蝕量值，以及沉積物自源區至流域出口的內部傳輸路徑。研究成果量化了流域內部沈積物緩衝作用，此作用使數十年尺度與千年尺度的侵蝕速率趨於一致。另外，DEM差分的空間分析成果可辨識出流域出口測站無法察覺的子集水區災害熱點。本研究展現了在氣候變遷下，未被充分利用的全球衛星DEM對於構造活動造山帶中沉積物相關地質災害監測的價值。;Sediment flux from active mountain belts records the coupled response of tectonics， climate， and surface processes， yet decadal-scale erosion patterns in steep， typhoon-impacted catchments remain difficult to resolve. Outlet-based gauging captures catchment-integrated yield but cannot reveal where sediment is produced， stored， or routed within a basin， while DEM differencing in these landscapes， which can offer alternate solution has been constrained by two persistent problems: stable-area based co-registration methods face challenges where stable ground is scarce， and elevation data carry noises such as vegetation canopy biases and sensor-induced artefacts that often exceed the geomorphic signal itself. This thesis develops and applies a DEM-differencing framework that addresses both limitations， and uses it to quantify decadal erosion and sediment redistribution in two mountainous catchments of Taiwan′s southern Central Range: the Zhoukou River (~375 km²) and the Laonong River (~1，373 km²). The first study introduces a Fourier-based spectral method for DEM vertical co-registration that identifies and removes vertical biases between repeat DEMs without relying on extensive stable ground. Applied to the Zhoukou catchment using open-source global and regional DEMs from 1990 to 2020， the corrected DEMs of Difference yield a decadal erosion rate of 14.19 mm/yr for the full three-decade window and 10.46 mm/yr for the most recent decade (2011–2020)， the latter reflecting a marked decline in extreme rainfall events. The declining DEM-derived rate in recent decade align well with independent suspended-load estimates from downstream gauge stations. The study shows that underutilized archival and satellite DEMs can deliver reliable decadal sediment budgets when the erosional signal dominates DEM noise. The second study extends the framework to the Laonong basin over 2000–2020， an interval that includes Typhoon Morakot (2009)， the highest-rainfall typhoon on record in Taiwan. Multiple global DEMs were benchmarked against airborne LiDAR， identifying NASADEM as the optimal archival DEM owing to its low spectral noise， minimal void-filling artefacts， and temporally coherent acquisition. Vegetation canopy bias， locally exceeding 30 m， was corrected using a global canopy-height model， followed by spectral vertical referencing; together these reduced volumetric uncertainty from ~187 to ~44 Mm³. Sub-catchment erosion rates average ~15.3 mm/yr and reach ~551 mm/yr in landslide-affected tributaries， yet 87.6% of the eroded mass is stored within the basin， predominantly as valley-fill deposits， alluvial fans， and trunk-channel aggradation. The resulting basin-wide net denudation rate is 5.06 ± 1.60 mm/yr， remarkably consistent with long-term (10³–10⁶ yr) cosmogenic and thermochronological estimates (~3–6 mm/yr) despite the occurrence of multiple extreme events. The result identifies sediment buffering as the mechanism that spatially averages localized extreme erosion at decadal timescales. Together， the two studies show that repeat topography， once vegetation and vertical biases are properly corrected， can resolve both the magnitude of decadal denudation and the internal routing of sediment from source to outlet. The framework reconciles decadal erosion measurements with millennial-scale rates by quantifying the role of internal storage， identifies sub-catchment hazard hotspots invisible to outlet gauging， and demonstrating the value of underutilized global satellite DEMs for monitoring of sediment-related geohazards in tectonically active mountain belts under a changing climate.
