## 1 Introduction  
Flash floods observed in northern France (and especially the Paris Basin) correspond to rapid and turbid flows that affect dry valleys. They occur following long winter rains or under the effect of violent storms [1; 2]. The structure of the landscape also plays an important role in these hydrological phenomena, both in the genesis of runoff and in its path through the basin. By landscape structure, we mean all the material objects that characterise the landscape and the interactions that link them, including the occupation of the land, the parcel of land, the boundaries of the parcels, the road system, etc. In the basins of the Pays de Caux, this landscape structure has changed considerably over the last few decades, leading to profound transformations. The main driving force behind these changes is the modification of agricultural practices, which intensified as they did throughout France during the second half of the 20 th Century. The landscape consequences, from which the Pays de Caux has not escaped, are the retreat of meadows and orchards, the increase in cultivated areas, the enlargement of cultivated plots, and the removal of features deemed obsolete: hedges and ponds, in particular. The move towards specialised cropping systems (maize, flax, wheat, etc.) at the expense of the traditional system (mixed farming) has contributed to increasing the vulnerability of the soil by leaving it bare during periods of heavy rainfall. Finally, this agricultural intensification has generated a proliferation of practices that weaken the soil by making it very sensitive to runoff and erosion. More generally, this rationalisation of landscapes is the cause for a more general degradation of the environment:deterioration of water quality, silting of rivers, impacts on aquatic habitats, and more generally on biodiversity [3; 4; 5]. Measuring the impact of this evolution on the sensitivity of basins to runoff and flash flooding processes is a major issue. Various previous works have been based on the use of distributed modelling tools to reproduce the flow of runoff on a slope or in small agricultural basins [6; 7; 8; 9; 10; 11; 12; 13; 14]. At the same time, many authors have studied in detail the impact of landscape organisation on the links between flow-producing areas and the overall hydrological behaviour of the catchment. This is the \"hydrological connectivity\" that characterises the interactions between the surfaces and networks that produce runoff and convey it to the outlet [15; 10; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29]. With the increase in computer memory capacity and the growing development of spatial analysis processes, methods derived from distributed artificial intelligence offer another alternative for modelling flow transfer in a watershed. These methods offer great possibilities. One of the most widely used approaches to simulate flow in a watershed is the cellular automaton (CA) [6; 30]. One of the first cellular automaton-based models applied to flow simulation was developed by [PERSON] and [PERSON] [31]. This work [31] was followed by the application of numerous cellular automata models in a wide variety of environments [32; 33; 34]. [PERSON] and [PERSON] [35] combined [PERSON]'s equation and the principle of conservation of mass to allow sufficient interaction to represent the movement of water in a river. They were able to simulate with some degree of accuracy a flood hydrograph that fairly represents the observed hydrograph. RuiCells [6] was developed for the simulation of erosive runoff phenomena within small watersheds and for intense turbid flood phenomena. Another approach to simulating flow in a watershed is the use of multiagent models, which differ from CA due to their use of a mobile entity called \"agent\". Multiagent models provide a different view of the temporal and spatial dynamics of the flow in a watershed. Unlike the cell used in a CA, the agent is mobile, and its environment will change depending on its movements.