<p>Beach nourishment is a widely used coastal adaptation strategy, though for some coastlines, debate exists as to its long-term viability to offset the impacts of sea level rise, due to limited sediment sources and negative environmental impacts. For beaches in bays and estuaries, wave energy is lower than the open coast, decreasing required nourishment volumes, and bay shorelines around large cities are often already extensively disturbed. We examine whether nearshore-sourced beach nourishment is a viable long-term option for a range of lower energy shorelines across Port Phillip Bay, Australia. Sand volumes were estimated from sub-bottom profiling (75&#xa0;km of shoreline to 2&#xa0;km offshore) and grain size was compared against beaches. Shoreline recession was estimated for 1&#xa0;m sea level rise to 2100, applying a variable depth of closure, ranging from a high-end ‘shoreface’ response (likely on moderate energy shorelines), to a low-end ‘beachface’ response (very low energy beaches). Offset nourishment volumes to maintain present-day beach width were calculated. Available sand volumes substantially exceeded projected offset nourishment volumes for 4 out of 5 zones. Moderate energy shorelines had sandbodies sufficient for long-term nourishment (c. 2400–4300 m³/km/year; &lt; 20% of available volume required). For very low energy beaches, sediment volumes were plentiful but may be less viable due to higher mud content. A comparison between long-term nourishment requirements estimates that bay beaches require c. 40–90% lower sand volumes than ocean beaches, due to reduced shoreface extent. Accordingly, coastal managers should consider incorporating long-term beach nourishment into nature-based adaptation strategies for bay and estuarine coastlines.</p>