The impact of the informal area expansion on the urban natural ventilation of Alexandria

The city plan of 1921 conducted by the British Sir MacLean was the first scheme of Alexandria in the modern age (Egypt). Applying the network planning basics, the scheme had created an ideal thermal environment for the coastal city; the perpendicular streets on the coast, main axes parallel to the sea and the availability of inner water surfaces, all have played a major role for providing thermal comfort to the deepest point of the city’s south borders in a successful form of cross natural ventilation effect on the urban level. Many changes have taken place on MacLean scheme during the past 90 years, most notable changes were the replacement of the water body (Lake Hadara) with a classy residential area (Smouha) along with significant shrinkage in Lake Mariout surface, accompanied with a huge informal housing expansion to the south, west and east of the city. Gated communities and the governmental affordable housing projects were also some of the major changes in the city. Surprisingly, among the changes of the city shape, only the informal housing expansion came out just like the old layout attributes of MacLean’s scheme with its environmental benefits. This paper is an investigative analytical comparison study depending on fieldwork where the collected air quality numerical measurements (i.e., CO, CO₂, relative humidity and particles matter) in the selected test area came out within the global standards. The wind characteristics have been analyzed to assess the real effect of the urban natural ventilation in Alexandria. The study argues that the network planning invented by the early builders of Alexandria and had been applied involuntary in the informal areas has turned to be the preferred layout. This provides a sort of ecological balance along with economic benefits by applying the urban natural ventilation concept, and therefore, better living conditions were provided and the air pollutants’ proliferation has been reduced.