how to assess the sustainability of an urban area?

i recently got to work on an interesting project. the challenge was to propose a method that would allow us to assess the sustainability of an urban area. now there are rating tools like LEED UD and CASBEE for Urban which are geared towards the rating of urban areas, but the whole topic is still very hazy with a lot of conflicting ideas.

what can be a good measure of sustainability? some people strong believe that it can boil down to carbon emissions. one some magic number. there is always this problem of trying to simplify things so that it becomes understandable, and another of oversimplification. often, we are all caught between a rock and a hard place.

urban areas would require consideration of the urban massing, the water management, waste management, transport and landscape. these would be the main areas what would impact the sustainability performance of a place i guess. as to what would constitute the component indicators that we can assess the performance, that is as good your guess as mine.

i realized that one problem within the sustainability realm is that consultants propose what they know and what they are familiar with. as a result, a lot of foreign standards are grafted onto a local site. i believe the principles of the workings behind a sustainability framework can be brought across different places with different climates and resources, but i'm not so sure if that is a good idea or not. if all sustainability is local, why are the standards universal?

guess this is an area which should be an interesting venue of research.