Abstract
Climate change is projected to cause considerable pressure on our environment and communities. In particular, an increase in flooding and extreme erosion events is foreseeable as a result of an anticipated increase in the frequency and severity of storms. In the absence of timely and strategic intervention, climate change is taking us closer to more uncertain (non-linear, stochastic) and potentially more catastrophic climatic impacts. This paper develops a state-of-the-art modelling framework to assess the economic impact of erosion hazards on critical infrastructure and evaluate their vulnerability and resilience to differing storm regimes. This framework is trialled on a UK town (Cockermouth, NW England) that has experienced significant storm-related erosion and flood damage in recent years, highlighting its ability to determine current and future erosion hazard to critical infrastructure. A hydro-sedimentary model is used to simulate fluvial and hillslope sediment erosion and deposition caused by extreme storms within river catchments (sheet, rill, gully and channel bank and bed erosion). The model is applied for current climate conditions and for two future epochs (2021–2040 & 2061–2080) to assess changing erosion hazard to critical infrastructure. Climate conditions for the two epochs are obtained using the UKCP18 high resolution realisation projections under emission scenario RCP8.5. The economic loss caused by these hazards is projected based on new, non-linear depth-cost curves derived from previous assessments. The results show that: 1) due to a warming climate, total rainfall in the Cockermouth area (and likely across the UK) may be higher for all storm durations and annual exceedance probabilities, until epoch 2061–2080 when the rainfall regime may shift towards shorter duration events with higher rainfall and longer duration events with less rainfall; 2) the total area that undergoes flooding, erosion and sediment deposition, and the magnitude of the hazard, may increase as the climate shifts; 3) the economic damage caused by erosion and deposition is positively related to rainfall total, and the highest costs are likely to be associated with damage caused to bridges (£102-130 million), followed by sediment deposition in the urban fabric (£9-82 million), and erosion damage to agricultural land (£16-26 million), buildings (£0.4-18 million) and roads (£0.4-4 million); and 4) the Estimated Annual Damage costs suggest that investment in bridges (£4-6 million) in the Cockermouth area is required now to ensure their resilience to extreme storm events, and interventions are likely to be needed within the next 20 years to prevent high economic costs associated with significant sediment deposition in the urban fabric (£0.3-4 million) and damage to roads (£0.08-0.1 million) and agricultural land (£0.6-2 million). This new framework can help support operational (immediate) and strategic (medium to long term i.e. 10+ years) erosion control decision making through the provision of an assessment of the scale and consequences of erosion.
Highlights
Climate change is projected to cause considerable pressure on our environment and communities (Kellogg, 2019; Araújo & Rahbek, 2006)
Numerous models exist for predicting river and slope erosion (e.g. Correa et al, 2016; Guan et al, 2016; Huang et al, 2016; Haregeweyn et al, 2017) and numerical studies have investigated impacts of land use and climate change on catchment-scale erosion and sediment yields (e.g. Boardman et al, 1990; Favis-Mortlock and Boardman, 1995; Howard et al, 2016), these have not resulted in an integrated compu tational framework with high capability to: (1) quantify the uncertainty in the risk posed by these hazards; (2) assess the impact of erosion hazards on critical infrastructure; (3) evaluate the physical and financial vulnerability and resilience of these assets to different storm regimes; or (4) communicate effectively these projections for decision support
The novelty of the modelling framework lies in the following three aspects: 1) hourly rainfall data from the recently released climate projections (UKCP18) is used to create DDF curves and corresponding hydrographs and hyetographs for the coming two epochs to drive a hydro-sedimentary numerical model; 2) a hybrid approach, which combines the strength of the reach mode and the catchment mode of the model CAESAR-Lisflood, is adopted so that erosion hazards in the both the hillslope and fluvial system are assessed; and 3) economic loss resulting from erosion damage is quantified for different land-use types based on new non-linear depthcost curves
Summary
Climate change is projected to cause considerable pressure on our environment and communities (Kellogg, 2019; Araújo & Rahbek, 2006). Major advances have been made in the prediction of flood risk and the assessment of the vulnerability and resilience of critical infrastructure to river and surface flooding In the UK, the Environment Agency provides publicly available maps with predicted risk of flooding from rivers, sea and reservoirs (Environment Agency, 2013; DEFRA, 2016). Boardman et al, 1990; Favis-Mortlock and Boardman, 1995; Howard et al, 2016), these have not resulted in an integrated compu tational framework with high capability to: (1) quantify the uncertainty in the risk posed by these hazards; (2) assess the impact of erosion hazards on critical infrastructure; (3) evaluate the physical and financial vulnerability and resilience of these assets to different storm regimes; or (4) communicate effectively these projections for decision support. Sustainable and resilient decision making for a changing climate is a challenge
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