One of the things you need to determine for an urban growth model is how much more development capacity is available on a property. In some situations this can be easy to find. For example a property with a single detached house that can be demolished and replaced with multiple attached dwelling units. The challenge comes when a property consists of common property with multiple attached dwellings or commercial units.
If you treat dwellings/units as individual properties when they are part of a larger building complex or site, there is every chance the attributes of these individual properties would not meet development density criteria that apply to that site. Thus, the model would determine no further development growth could occur at that site. In many instances these sites have further development potential. Some examples include: an old block of units that can be demolished and replaced with a high-rise unit complex; a site that is being developed in stages over several years and is only part way through delivery of those stages.
Where are the children?
To assess if sites can be further developed we “flatten” the cadastre. We do this by identifying the geometry of “common” property in the Digital Cadastral DataBase (DCDB). In the DCDBs we work with, most of these properties can be easily identified because they are also known as “Lot 0”. We call these geometries Master Property Lots (MPL) in our urban growth models. Next we establish if there are smaller property geometries inside the MPL geometry. We call these Child Lots. Unfortunately, not all common properties are assigned to Lot 0 and the DCDB still must be scoured for other property that has Child Lots.
The attributes of the Child Lots are combined and applied to the MPL in the model. These attributes include: number and type of dwellings; gross floor area; and type of land use. The Child Lots are then removed from the model. We can now apply the development density provisions and any development constraints to these MPLs and easily decide if there is further development capacity available at the site of the MPL.
Another advantage of method is it reduces the number of properties in the model, whilst maintaining the same level of information. We have seen this number reduce by up to 45% in some cases. Having a simpler urban growth model without losing accuracy is always a good thing.
It is very time consuming and complex to perform this task manually. Fortunately, Forecaz Modeller fully automates this task. This dynamically reduces the time required to prepare the urban growth model, whilst minimising any errors/deficiencies that are normally introduced when manually performing this task.