Designed by architecture students, Margaux Leycuras, Marion Ottmann, and Anne-Hina Mallette, from the architecture school of Nantes, they recently won a prize in a competition organized by the Foundation Jacques Rougerie - Institut de France. Their ‘Hydropolis’ proposal answers to this competition, in the category rising waters, by a project located in the Nile Valley which aims to exploit the phenomenon of rising waters instead of suffering the consequences.
In the past, the Nile Valley lived to the rhythm of the rise of the water level, taking the advantage offered by silt to fertilize its farmlands. However, these water variations are irregular, thus we witnessed periods of flooding followed by drought. Thus, the Egyptian government in 1902 began the construction of a dam seven kilometers upstream from Aswan to tame the river, creating a huge lake : the Lake Nasser, which floods part of the territory. This dam was consolidated many times and rebuilt completely in 1950.
This dam has a negative impact on the ecosystem. Indeed, the absence of silt in the valley no longer compensates marine erosion along the coast, causes a decline in the fishing and no fertilizes anymore farmlands. We are also seeing saline intrusion in the Nile Delta causing a precipitous coastline erosion. In addition, the rapid filling of the reservoir by the deposition of silt will saturate the capacity of the dam in less than a century, hence its inefficiency in the long term.
In order to solve these problems and restore the ecosystem in the Nile valley, we develop an alternative project to the Aswan Dam which takes advantages from the contributions of the flood while controlling the river. Then, we create a modular system of cities along the river Nile. So, we turn a technical problem into an ideal city.
The main idea of the project is to divide up the Lake Nasser into each city-modules in a reservoir lake of 200m deep. Thanks to this lake combined with a hydrological system, we succeeded to get a more natural flood level control. Each city is surrounded by the river Nile connecting all cities module together, by Egypt’s first communication system. These cities are formed of an enveloping sea wall adapting the topography of the mountain bordering the valley. From this dyke emerges a traffic flow (roads, bridges) linking the city with the outside (surrounding villages).
At the urban scale, the module is structured by a complex hydrological system. Indeed, the main fluvial axis, controlled by locks, crosses the city to reach the internal port area situated on the reservoir lake. In addition, the irrigation of the fields is provided by the combination of dikes, canals and valves. The whole converging towards the central reservoir lake, on its circumference is located a ring forming the city. It sets up on the bank surrounding the lake and extends on the water. Thus the city straddles between the land (agriculture) and the lake (exchanges).
Our hydrological system puts in accord the flood rhythm with the agricultural rhythm. From July to September, the Nile is in flood. The valves of the exterior dam are opened, then the water and the precious silt is deposited in the fields. The valves of the inside dam are also open in order to fill in the reservoir lake. Then the Nile returns to his riverbed, the lake reservoir is full and the water is retained by the interior dam of which the valves are closed. The valves of the exterior dam are also closed to irrigate and left fifty centimeters of water in the fields. This is the time of plowing, planting and semi rice shoots. For five months, the rice will grow its feet in the water. May is the month of harvest. Three weeks before we open the floodgates to the external dam, and the rice will finish its maturation out of the water. From June to July is the drought, drying and winnowing of the rice. Finally, at this time, the level of the Nile is at its lowest level but the city benefits from the water of the lake reservoir.