攔砂壩土壤有機碳儲存量評估框架之研究

Abstract

本研究旨在建立一套針對臺灣攔砂壩淤積地區有機碳儲存潛力之評估框架，結合二維水理模式、土壤分類與現地量測分析，以掌握不同壩體類型與地理條件下的碳儲特性。研究選定宜蘭縣員山鄉枕山村大礁溪封閉式攔砂壩(JX01)、宜蘭縣南澳鄉武雲溪封閉式攔砂壩(NA01)與新北市瑞芳區弓橋里開放式梳子壩(RF02)三處代表性攔砂壩為對象，運用 HEC-RAS 二維水理模式模擬淤積情形，獲得壩後淤積體積與面積，並配合實地採樣獲得之總體密度、有機碳濃度、總氮及細顆粒比例，估算各壩體的淤積有機碳儲量。 同時，參考臺灣各類土綱的碳儲資料與各壩實際分布之土壤類型，進行代表性有機碳濃度設定與整體碳儲量外推。為探討前30公分淺層碳濃度對整體碳儲的代表性，本研究建立上限與下限估算範圍，並與實測總量對比。結果顯示，三處壩體之有機碳總儲量推估分別為大礁溪(JX01) 35.085~54.296 Mg、武雲溪(NA01) 16.538~25.594 Mg、弓橋里(RF02) 13.383~20.711 Mg。 此外，本研究亦建立以土綱平均碳濃度與壩後淤積條件為基礎之簡化預測模型，提供可於樣區外初步評估之工具。整體而言，本研究結果指出攔砂壩不僅具水土保持功能，亦潛藏顯著碳儲潛力，其空間異質性則須納入壩體地形與土壤組成等因子考量，為未來國土碳管理策略提供依據。

This study aims to establish a preliminary assessment framework for estimating the soil organic carbon (SOC) sequestration potential in sedimented areas behind check dams in Taiwan. By integrating 2D hydraulic modeling, soil taxonomy, and field-based analyses, the research seeks to understand the carbon storage characteristics under different dam types and geomorphic conditions. Three representative check dams were selected as case sites: a closed-type check dam in Dajiao Creek, Zhenshan Village, Yuanshan Township, Yilan County (JX01); a closed-type check dam in Wuyun Creek, Nanao Township, Yilan County (NA01); and an open-type slit dam in Gongqiao Village, Ruifang District, New Taipei City (RF02). Using the HEC-RAS 2D hydraulic model, the post-dam sedimentation volume and area were simulated. These were combined with measured data, including bulk density, SOC concentration, and fine particle ratio, to estimate the SOC stock within the sedimented zone of each dam. In addition, representative SOC concentrations were assigned based on Taiwan’s soil order carbon storage database and the actual soil types distributed at each dam site. Extrapolation of total SOC storage was performed by setting upper and lower estimation bounds to evaluate the representativeness of surface (0–30 cm) SOC concentrations. The results indicated that the estimated total SOC storage for each dam was: JX01: 35.085~54.296 Mg, NA01: 16.538~25.594 Mg, and RF02 : 13.383~20.711 Mg. This study further developed a simplified predictive model based on average SOC values for relevant soil orders and dam-specific sedimentation characteristics, offering a practical tool for preliminary assessment beyond the sampled sites. Overall, the findings highlight that check dams not only serve sediment retention and watershed conservation functions, but also hold substantial carbon sequestration potential. However, spatial heterogeneity must be accounted for by incorporating dam morphology and soil composition into future national-scale carbon management strategies.