Wednesday, July 14, 2004

More fun with satellite photographs

This one is Sydney, Australia. The city has unusual constraints on its growth, that are much easier to show via a photo like this than any other way.

Firstly, a national park was declared to the south of the city about 150 years ago. Combined with other land that is legally protected from development in a couple of other ways and which is contiguous to it, this makes up the green patch that follows the coast to the south of the city and which sort of juts inland a towards the south of the picture. The section of coastal plane (with the visible lake in the middle it) to the far south of the picture near the coast, is the city of Wollongong, which is where I grew up. (I grew up in the section to the north of it where the coastal plain narrows). The body of water close to the coast just to the north of the green section is Botany Bay, and the river that goes inland from it is the George's River. To the north of that is another body of water, and this is Sydney Harbour itself.

In any event because the national park was declared to the south of Sydney, the city was not permitted to grow south along the coast as would be expected.

To the west of the city of Sydney we find another green section, which is the Blue Mountains. This is extremely rugged country, and the mountains form a natural barrier to the growth of the city to the west. The blue patch towards the south of the mountains is Lake Burragarang, which is an artificial lake that provides Sydney's water supply. A little to the north of that is a light line going through the mountains from west to east. This is the Great Western Highway, which follows a high ridge across the mountains. There are towns along the highway, and my sister (hi Leonie) lives in one of these towns. Just to the north of this you can see a very deep valley the name of which temporarily escapes me. There is another road across the mountains along the next ridge, bits of which are visible in the photograph if you look carefully.

Whereas the edge of Sydney in the south is very clearly defined, to the north the edge is less clear. This is basically because that part of Sydney north of the harbour is also rugged country, even very close to the ocean. One walks through fairly ordinary looking (and upmarket - this is a prestigious area in which to live) suburbs, and at the end of the street one find's oneself standing on the edge of an immense canyon. So Sydney north of the harbour is a mixture of residential suburbs and forest and National Park all mixed in together. As you go further north it is more National Park and less residential suburb. In essence, the parks form a barrier to the growth of the city in the north as well, but in a slightly less clear cut and sudden way than in the south. (In the north, urban areas resume again once an area of national park and rugged country has been passed. This area (around the city of Gosford) is visible at the far north of the photo.

This all makes Sydney a curiously constrained city. It can't spread east because of the ocean. It can't spread north or south close to the ocean due to mainly manmade constraints. It can't spread west because there are mountains. Which means that Sydney's urban sprawl in recent years has been in both the north-westerly and the south-westerly directions, leading to the curious triangular shaped city you see in the photograph.

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