STEP 3: DEVELOP A GROWTH POTENTIAL SURFACE

The historical growth trend portion of our study identified areas where development has occurred over the years. In developing a growth potential surface for the future, we thought it important to include existing attractors and detractors that may influence future development.

We developed a computer model that considers the influences of historical trends as well as attractors and detractors. We called our computer model "SMUG", the Suitability Model for Urban Growth. The result of this model is a distance analysis surface that classifies areas based on their potential for growth. Some areas are prime for development while others show very little potential for development. The areas are classified from lowest to highest on the final map, from the least amount of growth pressure to the highest amount of growth pressure. Behind the scenes we actually used numbers ranging from 1 to 9 to classify attractors. 1 represents the lowest possible attraction and 9 represents the highest possible attraction.

For detractors the classification ranged from 0 to 9 where 0 represents no detraction and 9 represents the strongest possible detraction. Detractors did not necessarily have values for the entire range from 0 to 9. If a detractor was considered severe enough, we simply included it in the exclusionary mask. The detractors we used were considered mild detractors and therefore only were assigned low detractor values, 0 to 3.

Before running the model, distance analysis surfaces were created for each attractor and detractor. The surfaces contained numeric values, ranging from 0 to 9, representing the strengths of attraction or detraction. Each surface could not be treated equally. The attraction of historical industrial land is not as important for future development as the attraction of vacant residential land. We decided to group the attractors into tracks, or groups of related features that can be weighted against one another. For example, the three historical surfaces were placed in a 'historical track'. Within this track we considered historical residential to be the most important surface, then historical commercial, and then historical industrial. We used a 60-30-10 ratio, meaning that historical residential would be twice as important as historical commercial and six times as important as historical industrial. These three surfaces were combined into one by our computer model, SMUG. SMUG applied the user-defined ratios to each surface. Values in the historical residential surface were multiplied by .60, values in the historical commercial surface were multiplied by .30, and values in the industrial surface were multiplied by .10. SMUG then generated a single surface for the track by adding the three surfaces together. All together five tracks were used in the model, four for attractors and one for detractors.

Back to Growth Group Main Page   Next Step