The Columbia River Littoral Cell (CRLC) (160 km in length) provides opportunities to compare competing accommodation space relations under different conditions of relative sea level change. The CRLC system includes abundant littoral sand supply from the large Columbia River, late-Holocene prograded beach plains and barrier spits (0.5–5 km in width), two large marine-dominated estuaries (Willapa Bay and Grays Harbor), and a high-wave-energy inner-shelf. Littoral sand accumulation rates in prograded beach plains and barrier deposits are based on paleo-shoreline positions that are dated by great-earthquake catastrophic beach retreat scarps (n = 10) from 0.3 to 5.0 ka. The retreat scarp timelines are mapped in across-shore GPR transects (n = 79), yielding timeline-bounded polygons (n = 247). The polygons are evaluated for littoral sand volume and bounding ages, yielding volume accretion rates (m³ ka⁻¹), which are summed for the four CRLC subcells; Clatsop Plains (27.4 × 10⁶ m³ ka⁻¹), Long Beach (19.8 × 10⁶ m³ ka⁻¹), Grayland Plains (15.9 × 10⁶ m³ ka⁻¹), North Beaches (11.7 × 10⁶ m³ ka⁻¹). Major submarine sinks of littoral sand, including the inner-shelf and large marine-dominated estuaries, are evaluated for increased littoral sand accommodation space that could result from potential future sea level rise of 1, 2 and 3 m during the next century or two. The estimated beach and nearshore sand erosion needed to fill the increased submarine accommodation space from a 2.0 m rise in relative sea level would result in averaged beach retreat values of ~0.7 km (Clatsop Plains), ~1.2 km (Long Beach), and ~ 1.3 km (Grayland Plains), about 30–50% larger than previous estimates based on the Brunn method. These catastrophic shoreline retreat distances (0.7–1.3 km) represent 25–50% of the present widths of prograded barrier spits and beach plains. They serve as warnings about future catastrophic beach erosion resulting from potential future SLR in other similar barrier spit and beach plain shorelines worldwide.

哥伦比亚河沿岸单元（CRLC）（长160公里）为比较不同海平面相对变化条件下竞争性住宿空间关系提供了机会。CRLC系统包括来自哥伦比亚大河的大量沿海砂石供应，全新世晚期的滩涂平原和障碍物（宽度0.5-5公里），两个大型海洋河口（威拉帕湾和格雷斯港）以及波能内架。沿海滩涂和屏障沉积物中沿海沙的堆积速率是根据古海岸线位置确定的，该位置的大地震灾难性海滩撤退赤道（n  = 10）从0.3到5.0 ka。退缩陡峭时间线被绘制在跨岸GPR样线中（n  = 79），产生时间线边界的多边形（n  = 247）。评估多边形的滨海砂体积和边界年龄，得出体积吸积率（m ³  ka ^-1），将其累加到四个CRLC子单元中；克拉索普平原（27.4×10 ⁶ m ³  ka ^-1），长滩（19.8×10 ⁶ m ³  ka ^-1），格雷兰平原（15.9×10 ⁶ m ³  ka ^-1），北滩（11.7×10 ⁶ m ³  ka ^-1）。评估了沿海底砂的主要海底汇，包括内层架和大型海洋支配的河口，以增加沿海底砂的容纳空间，这可能是由于未来一两个世纪海平面可能会上升1、2和3 m所致。从相对海平面上升2.0 m来填补增加的海底住宿空间所需的估计海滩和近岸沙土侵蚀将导致平均海滩撤退值约为0.7公里（克拉索普平原），〜1.2公里（长滩）和〜 1.3公里（格雷兰平原），比以前的Brunn方法估计值大30–50％。这些灾难性的海岸线撤退距离（0.7-1.3公里）代表了目前的扩展障碍口和海滩平原宽度的25-50％。