Case Studies Using Uplan SWIM Layers: Sierra Foothill

This case study is of a small area at 2500 feet in the Sierra Nevada on the Route 80 Corridor. The map is approximately 10 miles in height and 5 miles in width. At this scale, local roads and road names begin to appear.


Base Case Scenario

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This map shows the 2050 population projections from Department of Finance. Using existing general plan zoning, Uplan assigns growth levels within the existing zoning using Attractors and Discouragers. Attractors used in this scenario are economic; for example, Interstate 80 attracts more businesses and residential growth than areas with smaller roads and non-roaded areas.

At this scale, some of the downsides of running a model become apparent. For example, the area of higher density in darker yellow near the label "Rollins Lake" is a mismatch with the terrain. The zoning is for smaller parcels and higher density, which causes Uplan to project a higher population and a higher density. However, the steepness of the actual terrain is often more than 30% slope; while county zoning allows smaller lots in theory, another zoning element restricts development to slopes less than 30%. A model such as Uplan should not be made to project growth at this scale, particularly in foothill terrain where there are a plethora of site specific conditions which vary from ridge to ridge.

Limiting Factors for Disaster Risk: Flood and Fire

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Two Discouragers are added to the base case in this scenario — flood and fire. The assumption is that at some point insurance will not be available for those wishing to build in either high risk flood or fire areas, using the FEMA floodplains and the FRAP high fire hazard layers as masks (producing no growth).

There are no flood plain areas at this elevation. Fire risk, however, is a major concern in this area. Significant areas throughout the map area have been "masked" for development by the program due to the FRAP fire hazard rating. Almost all the areas in the base case scenario to the east of Route 80 shown for additional growth are now showing "no growth" due to fire risk.

Limiting Factors for Resources: Groundwater

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Groundwater is used as a limiting factor in this scenario, as an addition to the flood and risk Discouragers in the previous scenario. This area is a fractured rock area with spotty groundwater availability. The Uplan model generally has scaled back density due to the Discourager of fractured rock groundwater availability. This can be seen west of Route 80 where solid blocks of low density are downgraded to patchy areas of very low density.

Again, at this scale, the projections should not be used as site-specific predictions. Knowledge of the local geology and history of wells indicates that there are a few bands of very productive fractured rock geology for groundwater at wells no more than 200 feet deep, and some areas where there is little or no success with wells at as much as 1000 feet deep. While the map may indicate a trend due to the masking for a limiting factor, the level of detail at this scale is misleading.

Population Explosion

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The Population Explosion scenarios takes the Department of Finance 2050 year projections and adds 20%. A Discourager was applied in floodplains, but not in fire risk areas or fractured rock groundwater basins.

Without the limitation of fire risk or groundwater as a Discourager, and with a relatively high density zoning, this area shows a very high increase in population density. Again, an intimate knowledge of the area exposes the inappropriateness of using Uplan at this scale. The site specific terrain restrictions, the very real groundwater limitations, and lack of realistic road and access undermine the model projection.

The visual image of the model used at this scale will not convey the value of the model. Uplan is not designed to offer build-out predictions at this level; it is designed to demonstrate trends and pressures. In these representations, if the viewer has local knowledge, the maps become confusing and misleading.

Maximum Pressure

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This scenario is a combination of the population explosion (DOF+ 20%) with the addition of the Discouragers from fire, flood, and groundwater.

Due to the inappropriateness of scale, the combination of Discouragers with the population explosion scenario serves to exacerbate the confusing interpretation of the maps. The Maximum Pressure scenario shows a lop-sided build-out on one side of the ridge, which happens to be the more steep side of the ridge with less roaded access, hence is just not credible. Thus, while the scenario is intending to convey trends of increased growth within allowable zoning but with restraints of resource and risk limiting factors, the reader, if he(she) has knowledge of the area, will be simply confused.

The overall take-away from this exercise is that one needs to be very careful how these maps are used, and at what scale the message is useful, and when it is not useful.