The Dynamic Environmental Sensitivity to Change (DESC) project coupled cellular automaton (CA)
modelling from various backgrounds and produced the CAESAR-Lisflood-DESC (CLiDE) modelling
platform: a geomorphological simulator that allows a variety of Earth system interactions to be
explored. 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 the
Lisflood hydrodymanic model (Coulthard et al., 2013) to simulate channel and overbank flow, is used
as the platform kernel. The two dimensional modular design allows great versatility in the range of
simulated spatio-temporal scales to which it can be applied. CAESAR has been used to investigate a
variety of sediment transport, erosional and depositional processes under differing climatic and land
use pressures in river reaches and catchments (Hancock et at., 2011). The recent addition of Lisflood
to the code improves the representation of surface water flow within the model by incorporating
momentum. However, as with many landscape evolution models (LEMs), CAESAR over-simplifies
the 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 these
limitations, the non-Lisflood controlled surface hydrological processes within the CLiDE platform are
replaced with a bespoke distributed hydrological model that includes a groundwater model. This
hydrological model partitions rainfall between surface run-off and recharge to groundwater using a
soil water balance model, which is applied at each grid cell. To simulate groundwater flow to river
channels we incorporate a single layer finite difference model into the code. This solves the governing
partial differential groundwater flow equation using a forward time-stepping, or explicit, solution
method (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 exchange
of recharge and baseflow. In addition to the hydrological modifications, a debris flow component has
been added to the platform. The triggering aspect of this component is linked to simulated
groundwater levels