Face aux limites de la cartographie de la prospective spatiale et territoriale : cas des blocs-diagrammes des systèmes hydrologiques

Abstract

International audienceFrom a prospective exercise that aimed at assessing the evolution by 2030 of water resources in France (AQUA 2030 French Ministry of Ecology), several territorial prospective scenarios were conducted. The preservation of aquatic environments and water as well as risks associated with it are the subject of public policies, but their joints with dynamic socio-economic and territorial issues can be complex and difficult to understand. From prospective workshops, scenarios aimed firstly to establish qualitative stories of the evolution of natural and human systems related to water in 2030, and secondly to cartographic representations of these systems territorially, to compare the states and allow debate on the issues. Seven spatial hydrological systems with five future states were built, with a need to represent 42 maps. These seven models have been selected according to their ability to illustrate dynamics and evolutions of the main hydrographical systems and water resource in France. As the seven spatial hydrological systems were chosen as 'ideal types', their cartographic representations encountered some limits. The paper presents these limits and a solution to optimize the spatial representation of these systems, with landscape block diagrams. The landscape block diagram can be defined as a 3D graphic representation of a landscape pattern. If maps are all the time connected to geographical coordinates, the blocks diagram can be not. It becomes an abstraction, a model of several real landscape patterns and ecological systems at different scales. To create a landscaped block diagram means having a degree of abstraction for representing the intermediate reality, both visual (concrete) and synthetic (simplification of forms and volumes, symbolic figure not viewable areas trend modeling). It aims to reflect on what can happen (prospective), not what will happen (forecast). At the spatial scale representations of the human's eye and understanding of landscapes, some punctual landscape components are difficult to read, or cannot be represented on a map. The model realized for this study represents a combination of spatial components describing some specific landscapes and hydrological systems themselves linked with the indicators of the five scenarios from AQUA 2030 report. Seven blocks have been designed as a model of typical French landscapes and 'ideal type' hydrographical system: seacoast and continental wetlands, mountainous areas as head of river basin, urbanized seacoast, urbanized riverside, intensive farming areas on plain, extensive farming systems on piedmont. 42 blocks were created at all: for each system a visualization of today following by 5 scenarios illustrating, ecological and socio-economical impacts or stakes thought landscape patterns and spatial components. The paper discusses how landscape blocks diagrams can be used as tool to compose, discuss, recompose the scenarios of the future water management instead of maps. Landscape visualizations translate a technical vision of indicators into a more sensitive vision of the scenarios understandable by everybody. The block diagram tool can serve as an educational mean in the service of a policy development project because it refers to experiences and practices witch create always new forms of the lands, then new ways to manage and their stakes