Frame 3. An account of experiments and debates about flood mitigation with a floodplain model The area (a) is the first flooded zone. A child notices that the narrow arch of the bridge acts as a stopper with a small hole. We observe that it aggravates the flood upstream in (a). We debate together about this solution: “Can we remove the bridge or change it for an other with wider arches ?” We ponder about the cost. They try it anyway, and see that now (b) is more easily flooded. Another child proposes to build a levee. He first makes one parallel to the river, and finds out that it is more efficient to surround the village (Photo 1). But once again the town (b) is more easily flooded. So the problem is moved to downstream. Then we will probably have to continue building levees all along the river. The children have understood that planning must be done at catchments scale. A child suggests to move the houses. Indeed, why not buy them rather than building protection structures, if it is cheaper? Let us now place a narrow-arched bridge upstream in a suitable uninhabited area (Photo 2). The children have (re)invented dry dams. But there are many different ways to look at a mitigation project. Each child is now assigned a role: one of them is a riverside resident; another is a farmer; a third one defends the ecological value of the river and the wetlands. The young mayors of the village and of the town have to please their electors but will have to pay the bills for the flood control structures. In contrast to the math's exercises they are used to, the children realise that there is no obvious unique “good answer”. References Navratil O., Poulard C., 2005, Retour d’une expérience et proposition d’un module sur le thème « Vivre avec les inondations », Cemagref, 50p. A first version is available at: http://oldrich.navratil.free.fr/publications Poulard C., Navratil, O., 2005, Une maquette de bassin versant interactive pour exposer au grand public les principes de prévention des inondations et de développement durable ; Algerian Journal of Technology, tome 1, pp 11-19. Presentations are described at www.lyon.cemagref.fr/hh/hydrologie/scientifiques/poulard/maquette.shtml RESEARCHERS SHOULD CONVEY THEIR KNOWLEDGE ABOUT FLOODS – BUT HOW? Floods are the most common natural risk in France. Current national policies put forward the need to increase flood awareness to the civil society. We therefore responded positively to an invitation to give talks in a primary school (8-10 years old children). We chose to explain flood processes and to comment on flood mitigation techniques. We developed an educational module (Navratil et al., 2005) focused on both scientific contents and method (13 sequences of 45 min. each). Proceeding by stages allowed us to adapt our talks to the children’s knowledge and expectancies, and to develop the approach best suited to them. Hands-on experiments and interactive tools are known to stimulate the curiosity of children. We therefore designed a set of experiments to help them go through the process of hypotheses, test and understanding. THE EDUCATIONNAL MODULE The module focuses on the: Acquisition of the main scientific contents... • Back to basics with the notions of discharge and volume; • Relations between rivers and human activities; • Floods are part of the natural water cycle; • Floods are sometimes useful (e.g. ecological value of wetlands) or acceptable (better let the water overflow here than in the village); • Flood mitigation, its limits and its impacts. ...within a scientific methodological framework... • With an active learning method in small work groups, hypothesis formulations and tests with experiments; • Results are presented and discussed with the whole class, to draw common conclusions. ...through various media developed or adapted for the module • Questionnaire to evaluate what they know at the beginning and at the end of the module (see frame 1) • Experiments (see frame 2); • Posters (see frame 2); • A physical model (Poulard et al., 2005) of a river and its floodplain (see frame 3). CONCLUSION AND PERSPECTIVES The implication of children helped a lot to develop a really attractive and informative module. Our floodplain model has been used to discuss many issues, including non-structural measures. It was designed for presentations towards both children and adults during scientific meetings. It is also a good tool to promote flood awareness (and risk culture), and could be useful for local authorities. However, models must be carefully designed to meet the specific objectives and constraints. For instance, is the issue to convey basic messages about flood risk and flood mitigation, or to initiate a debate with stake-holders ? To our opinion, a simplified model such as ours is a good tool. If the goal is to inform inhabitants about already planned structures, it can be tempting to dream of a scale-model with a realistic topography. However, ensuring realistic behavior of flows would require very costly hydraulic studies. TESTING IN WORK GROUPS... Hands-on experiments Simple experiments were devised to transmit the basic concepts in hydrology unknown to children and necessary to study the floods. For example, the notion of volume and discharge were illustrated by pouring out water from a bottle into half bottles of different size and different hole size in the stopper (see frame 2). Posters Posters are useful support to discuss together. One exercise consists in comparing the previous experiment with a river basin poster (see frame 2). We made an analogy between the bottle filling and the river basin. A floodplain model To the question asked: “How can we study floods?”, a child answers: “We have to be present on the field when flood is happening or we can reproduce the reality”. Following his last idea, we developed a floodplain model where floods can be called at will. Interactive experiments were led in six steps to answer to the following questions: •”What is a physical model?”; •“Why floods occur?”; •“Where do floods occur?”; •“What are the consequences for human activities?”; •“What are the flood mitigations we can propose/test?”, see frame 3. ...AND DEBATING TOGETHER TO LEARN Class and groups debates are essential steps in this module. Debates are required when children need to put their ideas or results in common. They are animated by the teacher or schoolchildren themselves. So they permit to draw the main conclusions together after each experiment or each group work before continuing with other experiments. Frame 1. Examples of questions asked and children answers in the questionnaire •Are there rivers in the city of Lyon ? An answer : « The Saône and the Rhône Rivers. » •Why did people settle next to river ? « To study them. » •Do floods happen only in the cities ? « No, everywhere. » •Since when floods occur? « Since the Dinosaur period ». a b Photo 2 Photo 1 Frame 2. Analogy between a river flood and a bottle filling experiment With the bottle experiments, children identified four main factors that control the bottle filling. Next, we made a comparison between the bottle experiments and observation of a picture of a river flood: •The quantity poured  the rainfall volume; •The way we put the water in the bottle  rainfall intensity; •The half bottle capacity  the main channel size before overflow; •The hole size in the stopper  obstacles (logjams, bridges, etc.). We also look for differences: the size, the time for the water to reach the outlet. Development of a module in hydrology to transmit the principles of flood mitigation to schoolchildren O. Navratil (1), C. Poulard (2) (1) IRD-LTHE, Grenoble, France (www.lthe.fr), oldrich.navratil@hmg.inpg.fr ; (2) Cemagref, Lyon, France (www.cemagref.fr), christine.poulard@cemagref.fr