The U.S. Pacific Northwest (PNW) coastline (1000 km) has been analyzed for conditions that could impact beach erosion from potential near-future (100 year) sea level rise (SLR). Heavy mineral analysis of river, beach, and shelf samples (n = 105) establish the sources of the beach deposits. River bedload discharge and intervening estuarine sinks for river sand supplies (n = 31) were normalized to the one century time interval. Twenty-six subcell beaches (657 km in combined length) were surveyed (153 profiles) for beach sand widths (20–412 m) and sand cross-sectional areas (20–1810 m²) above wave-cut platforms and/or 0 m tidal datum. Cross-sectional areas were multiplied by beach segments to yield subcell beach sand volumes (0.4 × 10⁶ m³–35.8 × 10⁶ m³ ± 20% uncertainty). Innermost-shelf profiles were measured for distance to the 100-year depth of closure (30 m) to digitize the areas of inner-shelf accommodation space. Both innermost-shelf and estuarine accommodation space volumes for beach sand displacements were established for 0.5 and 1.0 m SLR. The existing subcell beach sand volumes and computed new beach sand supplies (rivers and longshore transport) were subtracted from the estimated sand volumes lost to submarine accommodation spaces to establish potential beach sand deficits from near-future SLR. Of the 26 surveyed active-beaches, some 60% and 80% (by length) are predicted to be lost, respectively, from the 0.5 m and 1.0 m SLR or equivalent littoral sand sedimentation in submarine accommodation spaces. Projected losses reach 90% for all PNW beaches (~900 km total length) from 1.0 m SLR. The computed beach sand deficits are used to estimate soft-sand retreat distances or erosional beach step backs (50–590 m ± 35% uncertainty) in unrevetted barrier spit and beach/dune deflation plains from 1.0 m SLR. Such empirical accommodation space analyses should have worldwide relevance to predicting beach erosion from near-future SLR.

美国太平洋西北部 (PNW) 海岸线 (1000 公里) 已经过分析，以了解可能因近期（100 年）海平面上升 (SLR) 而影响海滩侵蚀的条件。对河流、海滩和陆架样品 ( n  = 105) 的重矿物分析确定了海滩沉积物的来源。河流底泥排放和河沙供应的干预河口汇 ( n  = 31) 被标准化为一个世纪的时间间隔。对 26 个子单元海滩（总长度 657 公里）进行了调查（153 个剖面），用于确定波浪切割平台上方的海滩沙子宽度（20-412 m）和沙子横截面面积（20-1810 m ²）和/或 0 m 潮汐基准。横截面积乘以海滩段以产生亚单元海滩沙体积（0.4 × 10 ⁶米³ –35.8 × 10 ⁶米³ ± 20% 不确定性）。测量最内层货架剖面与 100 年关闭深度 (30 m) 的距离，以数字化内层货架住宿空间的面积。为 0.5 和 1.0 m SLR 建立了用于海滩沙置换的最内层搁板和河口容纳空间体积。现有子单元海滩沙量和计算出的新海滩沙供应量（河流和沿岸运输）从估计的水下住宿空间损失的沙量中减去，以确定近期 SLR 的潜在海滩沙量不足。在所调查的 26 个活动海滩中，预计分别有 60% 和 80%（按长度计）来自 0.5 m 和 1.0 m SLR 或潜艇住宿空间中等效的沿海沙沉积。从 1.0 m SLR 开始，所有 PNW 海滩（总长度约 900 公里）的预计损失将达到 90%。计算出的海滩沙子赤字用于从 1.0 m SLR 估算未修整的障碍沙口和海滩/沙丘紧缩平原中的软沙后退距离或侵蚀海滩退步（50-590 m ± 35% 不确定性）。这种经验性的住宿空间分析应该在全球范围内与预测近期 SLR 的海滩侵蚀有关。