Sediment yield from the tectonically active semiarid Western Transverse Ranges of California
Sediment yield from the tectonically active semiarid Western Transverse Ranges of California
复制标题
加利福尼亚州构造活跃的半干旱西部横断山脉的沉积物产量
DOI：
10.1130/b26452.1
复制
发表时间：
2009
影响因子：
4.9
通讯作者：
L. Mertes
中科院分区：
文献类型：
--
作者：
J. Warrick;L. Mertes
世界河流的泥沙产量通常最高的是岩性较弱、构造活跃或土地利用影响严重的陡峭流域。在这里，我们评估加利福尼亚州西横山脉的沉积物产量，试图解释为什么它们比加州周围地区大两到十倍。我们发现，在1969-1999年间，西横断山脉测量的盆地的悬浮泥沙产量变化了大约一个数量级(740-5300吨/平方公里/年)。同样，在圣伊内斯山脉的11个以前未监测的水系中，归一化流量的细泥沙浓度变化了近两个数量级(例如，年平均洪水为1.3-110g/L)。产沙量高的地区基岩(第四纪-上新世海相地层)始终处于弱固结状态，并与该地区最高的构造抬升速率(>；5毫米/年)有关。这些区域对输沙平衡很重要，因为西侧向区域的悬沙流量估计有50%来自这些区域，尽管它们只占流域总面积的10%左右。之前对文图拉河悬浮泥沙流量的估计可能被低估了约50%，因为测量站位于高产沙区的上游。我们还发现，产沙量与草地和农用地分水岭的百分比呈显著正相关。这些结果表明，在更广泛的西横山脉地质省的岩性、构造和土地利用方面存在着足够的差异，从而在当地尺度上引起了很大的产沙量差异。
Sediment yields from the world's rivers are generally highest from steep drainage basins with weak lithology, active tectonics, or severe land-use impacts. Here, we evaluate sediment yields from the Western Transverse Ranges of California in an attempt to explain why they are two- to tenfold greater than the surrounding areas of California. We found that suspended-sediment yields across the gauged basins of the Western Transverse Range during 1969–1999 varied by approximately an order of magnitude (740–5300 t/km2/yr). Similarly, fine-sediment concentrations for normalized discharge rates varied by almost two orders of magnitude (e.g., 1.3–110 g/L for the mean annual flood) for 11 previously unmonitored drainages of the Santa Ynez Mountains. Areas with high sediment yields consistently have weakly consolidated bedrock (Quaternary-Pliocene marine formations) and are associated with the highest rates of tectonic uplift of the region (>5 mm/yr). These regions are important to the sediment discharge budgets, because ~50% of the total suspended-sediment discharge from the Western Transverse Range is estimated to be generated within these regions, even though they represent only ~10% of the total watershed area. Previous estimates of suspended-sediment discharge from the Ventura River have likely been underestimated by ~50% because the gauging station is located immediately upstream of a high sediment yield region. We also found a significant and positive correlation between sediment yield and the percentage of a watershed with grassland and agricultural land use. These results suggest that there is adequate variation within the lithology, tectonics, and land use of the broader Western Transverse Range geologic province to induce large variations in sediment yield at the local scale.