UKCP18 marine report

British Geological Survey

关键词: GroundwaterBGS;    Groundwater;    Groundwater modelling;   

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来源: NERC Open Research Archive

【 摘 要 】

The Dynamic Environmental Sensitivity to Change (DESC) project coupled cellular automaton (CA)modelling from various backgrounds and produced the CAESAR-Lisflood-DESC (CLiDE) modellingplatform: a geomorphological simulator that allows a variety of Earth system interactions to beexplored. A derived version of the well established Cellular Automaton Evolutionary Slope and River(CAESAR) model (Coulthard and Van De Wiel, 2006), CAESAR-Lisflood, which incorporates theLisflood hydrodymanic model (Coulthard et al., 2013) to simulate channel and overbank flow, is usedas the platform kernel. The two dimensional modular design allows great versatility in the range ofsimulated spatio-temporal scales to which it can be applied. CAESAR has been used to investigate avariety of sediment transport, erosional and depositional processes under differing climatic and landuse pressures in river reaches and catchments (Hancock et at., 2011). The recent addition of Lisfloodto the code improves the representation of surface water flow within the model by incorporatingmomentum. However, as with many landscape evolution models (LEMs), CAESAR over-simplifiesthe representation of some of the hydrological processes and interactions that drive sediment transport.Specifically, it does not simulate groundwater flow and its discharge to rivers. To address theselimitations, the non-Lisflood controlled surface hydrological processes within the CLiDE platform arereplaced with a bespoke distributed hydrological model that includes a groundwater model. Thishydrological model partitions rainfall between surface run-off and recharge to groundwater using asoil water balance model, which is applied at each grid cell. To simulate groundwater flow to riverchannels we incorporate a single layer finite difference model into the code. This solves the governingpartial differential groundwater flow equation using a forward time-stepping, or explicit, solutionmethod (Wang and Anderson, 1982), which can be considered as a cellular automaton (CA) model(Ravazzani et al., 2011). The groundwater model is coupled to the surface model through the exchangeof recharge and baseflow. In addition to the hydrological modifications, a debris flow component hasbeen added to the platform. The triggering aspect of this component is linked to simulatedgroundwater levels.