The Impact of Urban Fabric on Natural Ventilation for the City of Alexandria

Abstract

Alexandria is one of the most famous cities on the Mediterranean Sea. Many ages have passed over the ancient city and formed huge changes in the urban fabric, until the time came up with the first scheme of Alexandria in the modern age by the British Sir MacLean in 1921. By adopting the principles of the network planning, with perpendicular streets on the coast and parallel to the winds’ directions; MacLean was able to create the ideal thermal environment of the coastal city. With water surface (Mahmoudya canal) mediated the fabric and by maintaining the Lake of Hadara, the city achieved the cross natural ventilation effect of the urban fabric level providing the thermal comfort in the deepest point to the south, away from the coast. Unfortunately, many changes have taken place on MacLean scheme during the past ninety years. The lake had been totally replaced with a classy residential area (Smouha) along with huge informal housing expansion to the south-west and east of the city. While Smouha followed a completely contrary pattern, the informal housing expansion came out as the same as the old layout attributes. Smouha became a classy residential hot zone surrounded by informal housing areas enjoying better natural conditions. This paper is an investigative comparison study depending mainly on a fieldwork. The collected air quality numerical measurements of CO, CO₂, levels of humidity and particles matter that came out within the global standards, were used along with the winds’ characteristics to assess the real effect of the natural ventilation of the urban fabric. The study has proven that the network planning invented by the early builders of Alexandria has still the preferred layout accommodating the incoming air flow into the city in which the natural ventilation is playing an important role of providing better living conditions and reducing the air pollutants’ proliferation.