‘Development which meets the needs of the present generation without compromising the ability of future generations to meet their own needs.’
World Commission on Environment and Development(WCED), 1987

The WCED characterized the ecosystem according to three different sectors: economy, equity, environment. They stated that for this state of sustainability to be achieved there must be an understanding of the importance of balance between the three sectors in all development decisions. Therefore the challange for researchers, and the goal of this project, is to define a sustainable indicator set for spatial areas, which can be used in the management of the urban area to gauge the well-being of the city.

Sustainability Indicators are more comprehensive, consistent and descriptive than other methods of assessment of our urban environment. The indicator Gross Domestic Product (GDP), for example, is lacking in factual representation of the well-being of a society. The GDP is a national accounting system, which lumps all of societies ills along with the positives into one set of measurements for well being.

The GDP measures the consumption of natural resources without regard for use. An example would be housing and food, which are social goods and count positively towards the GDP. Disposal of waste from fertilizer manufacturing or construction waste from the housing industry are environmental problems with a cost involved but does not affect the GDP. GDP can be characterized as a single use indicator which is equally as problematic as other economic indicators such as the Gross World Product, which computes output of goods and services; International Trade, which monitors exports; Employment, which measures numbers of new jobs; and Stock Prices, which computes rise in prices on the Stock Exchanges.

An alternative to the GDP is a sustainability indicator called the Genuine Progress Indicator (GPI), which starts with calculating personal consumption expenditure. It then makes adjustment for negative effects of economic activity ignored by GDP, such as foreign borrowing; social costs such as crime and commuting; and environmental costs such as pollution. It then adds benefits ignored by GDP such as housework and parenting, services of highways and streets. The GPI is directly comparable to the GDP, which is its strongest benefit. However it suffers from making assumptions on costs and benefits for goods which have no market value.

Sustainability Indicator Systems are composed of various structures; requirements; and frameworks. The structure of indicator systems differ by: spatial assessment level; number of levels between indicator and subsystem; and whether they are aggregated to produce indices. Indices make observations easier to interpret; they provide key relationships; and facilitate analysis of critical strengths and weaknesses.

The requirements for indicators chosen for analysis is highly variable among practitioners in the field and at the same time there is convergence on some key themes.
Requirements for Indicator sets:
a. parsimony - the final indicator report should be as simple as possible.
b. scope - the indicators should cover the whole spectrum related to economy, socety and environment.
c. quantification - the elements should be readily measurable.
d. assessment - the elements should be capable of representing performance trends.
e. sensitivity - the chosen indicators should be sensitive enough to changes in the target area.
f. timeliness - frequency and coverage of the elements enable timely identification of the performance trends.

In order to find the balance between the systems of sustainability, frameworks are used.
The three major frameworks are:
a. categories
b. goal-indicator matrix
c. driving force-state-response matrix.

Categories simply list indicators by the categories of economy, environment and social. Problems with this framework are that some indicators are not easily categorized such as families in poverty, which can be either economic or social. In addition, this framework produces the false notion that the ecosystem is made up of three distinct categories, which is not properly representative since there are many important linkages that should be addressed.

The goal-indicator matrix is useful for showing the relationship of indicators to goals. Conversely it shows which indicators are relevant to adopted goals by a community. The problem with this is that we rely too heavily on one indicator to achieve a goal, which refutes the complexity of our human environment.

Driving force-State-Response Framework also called Pressure-State-Response, shows connections between elements in a community. The driving force or pressure expresses the changes in the level of use or state of the function. A ‘state’ of a problem is stated in terms of an indicator and then ‘responses’ are identified or causes of the ‘state’. An example is the ‘state’ of air pollution which has the ‘response’ of standards of fuel being set; auto emission standards; and car pools being set up. The ‘driving force’ for the ‘state’ of air pollution is simply too many people driving too many miles in too many cars.

Driving force-state-response frameworks are often used with the categories framework to make it easier to understand. The problem with this setup is that balance is not usually a top priority. This project utilizes a mixture of these frameworks since goals are the basis for the Houston SIP. The goals can be considered driving forces for which indicators will be developed to measure the state. The indicators will be developed with balance in mind. Responses will take the form of reports, plans, policies and projects based on accumulated data findings.