Abstract Water surface level exceedances and extreme flooding for Australia's most exposed estuary, Swansea Channel, was estimated using sea level rise epistemic uncertainty with symmetric and asymmetric shapes. Flood estimates were obtained using a simple hydraulic model what was applied within a statistical simulation, included atmospheric and oceanic forcing and their aleatory uncertainties. These predictions are then used to discuss vertical allowances for coastal planning. There are different allowance approaches to include sea level rise epistemic uncertainty ranging from asset independent (allowance includes a particular degree of sea level rise uncertainty) to asset specific approaches (allowance that ensures frequency of inundation does not increase). Regardless of the allowance approach, the sea level rise uncertainty distribution and its shape are expected to influence these allowances. The impact on flood estimates and derived allowances from symmetric and asymmetric uncertainties includes expected features of increasing water level variations and allowances in both time and in space (Swansea Channel becomes more hydraulically efficient as its depth increases). Using asymmetrical shaped uncertainty for coastal planning constrained by low risk tolerance would, for example, increase the 1% annual exceedance probability flood elevation that includes 99% of sea level rise uncertainty by ca 0.8 m along Swansea Channel when compared to symmetric uncertainties. If the future sea level rise uncertainty is indeed asymmetric then application of allowances based on the symmetrically shaped distributions underestimate possibilities of future extreme water levels and may be exceeded earlier than anticipated. Annual exceedance duration estimates indicate that in 2120, epistemic (sea level rise) uncertainty is greater than aleatory (weather related flooding) variational along Swansea Channel.

中文翻译：

---

考虑澳大利亚最暴露的河口海平面上升的不确定性：不同认知不确定性下的配额讨论

摘要 使用对称和非对称形状的海平面上升认知不确定性来估计澳大利亚最暴露的河口斯旺西海峡的水面水平超标和极端洪水。洪水估计是使用一个简单的水力模型获得的，该模型应用于统计模拟，包括大气和海洋强迫及其偶然的不确定性。然后将这些预测用于讨论沿海规划的垂直余量。有不同的允许方法来包括海平面上升认知不确定性，从资产无关（允许包括特定程度的海平面上升不确定性）到资产特定方法（确保淹没频率不会增加的允许）。无论采用何种补贴方式，预计海平面上升的不确定性分布及其形状会影响这些容许量。对称和非对称不确定性对洪水估计和衍生允许量的影响包括水位变化和时间和空间允许量增加的预期特征（斯旺西海峡随着深度的增加而变得更具水力效率）。例如，与对称不确定性相比，对受低风险容忍度约束的沿海规划使用不对称形状的不确定性将增加 1% 的年度超标概率洪水高程，其中包括 99% 的海平面上升不确定性，沿着斯旺西海峡增加约 0.8 m。如果未来海平面上升的不确定性确实是不对称的，那么基于对称形状分布的配额应用会低估未来极端水位的可能性，并且可能比预期更早地超过。年度超标持续时间估计表明，在 2120 年，认知（海平面上升）不确定性大于斯旺西海峡的偶然（与天气相关的洪水）变化。