Table 2: Climate change projections and their relevance for stormwater design
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| Type of change | Range of changes for 2030s | Range of changes for 2080s | Relevance for stormwater planning | Possible additional expertise and in-depth studies |
|---|---|---|---|---|
| Increase in heavy rainfall | Return frequency increases with temperature (up to twofold - specific figures in Table 2) | Return frequency increases with temperature (up to fourfold - specific figures in Table 2) | Increase in total rainfall depth for design storm events for durations of up to 72 hours | More complex rainfall modelling (e.g. RAMS model) or dynamic time series modelling |
| Change in annual mean rainfall | -19 to +22% (depending on region) | -32 to +57% (depending on region) | Change in antecedent soil moisture saturation | Modelling of soil moisture saturation for pervious catchment areas |
| Increase in annual mean temperature | 0.1 to 1.4°C (with some dependence on region) | 0.2 to 4.0°C (with some dependence on region) | Change in evaporation from soils and ponds, which changes antecedent soil moisture saturation | Modelling of soil moisture saturation for pervious catchment areas |
| Increases in wind | Not quantified: highly location specific but with a trend nationally to increased westerlies | Not quantified: highly location specific but with a trend nationally to increased westerlies | Changes in rainfall over complex topography – increases upwind of hills and ranges | More complex airflow and rainfall modelling (e.g. RAMS model) |
| Sea level rise | 0.2 m | 0.5 m | Changes to stormwater discharge, saltwater intrusion in coastal zones |
Note: Figures provided in this Table should only be used for a preliminary screening assessment; if based on this preliminary assessment the effects of climate change are potentially significant, a more in-depth assessment using additional expertise should be carried out. Table adopted from MfE (2004a) and MfE (2004b).
