Development of a Small Watershed Around Oak Grove

Development of a Small Watershed around Oak Grove

This study of alternative policies to guide residential development was conducted by graduate students in the Department of Landscape Architecture and Environmental Planning at Utah State University. It focuses on a relatively small and undeveloped watershed in the headwaters of Temecula Creek, part of the Santa Margarita River Basin. The area is designated as "Oak Grove," after a small rural community located near its center and is shown in figure 108. The distribution of land use in this study area will be based primarily on the existing building codes and zoning policies of this part of San Diego County.

Oak Grove could receive up to 1,500 new residents by the year 2010. To accommodate this growth, three development scenarios using different housing densities and associated land uses such as commerce, public institutions, and parks were created.

Three constraint sets for each scenario were then postulated and a comparison made of the benefits and risks to biodiversity of the density and constraint combinations.

Scenario Set A allocates all residential development for 1,500 persons at a rural residential density of two units per hectare.

Scenario Set B allocates development for 1,500 persons at rural residential density with some single family residential density at ten units per hectare.

Scenario Set C assumes establishment of a large industry within the site, resulting in a larger population increase of 5,000 residents. This scenario allocates development in a mix of rural residential and single family residential densities. This scenario attempted to determine the carrying capacity of the site.

The nine alternatives in figure 112 were then compared via hydrologic and biodiversity models. The runoff model demonstrated an insignificant change from development compared to present conditions. Even C2 and C3, which accommodate over twice the population of the A and B scenarios, show an insignificant increase in runoff, as seen in figure 113.

The habitat models were effective when used for determining the placement of development, as seen in figure 114. This is evident even in the final "three" scenarios, in which biodiversity-determining conditions were maintained.

Two caveats should be considered: The "Oak Grove" case studies did not consider water needs, the requirements for sewage treatment, or fire management. These issues require further study to make definitive recommendations. It may also be the case that these results cannot be universally applied throughout the greater Camp Pendleton study area due to the steep slopes and public lands that characterize much of the Oak Grove watershed.

The study however, indicates that current San Diego County land use regulations Ðif enforcedÐ do provide a substantial degree of protection for biodiversity. Impacts to biodiversity through direct removal of habitat or an altered hydrologic regime can be lessened substantially through steep slope restrictions, conservation of natural riparian floodway buffers, and public land protection.