SITE-WIDE STRATEGIES | STORMWATER MANAGEMENT

To address certain challenges on the scale of the entire site, certain site-wide design strategies are proposed. One major challenge that is present on all aspects of the site is stormwater management. Tubac as a village has no municipal stormwater management, and as the State Park is located between the village of Tubac and the Santa Cruz River beyond, that means that the site receives a lot of water, both on-site and from the village streets above. Capturing that stormwater is an excellent opportunity to offset the costs of irrigation throughout the course of the year, while providing an educational opportunity for locals and visitors alike in the central tenets of rainwater harvesting and stormwater management. Capturing and managing will also mitigate many of the problems associated with major rain events, including erosion of the site grounds and archaeological remains, flooding (especially around building footprints), basal erosion of adobe structures, and so on.

There are several recommended strategies for the Tubac Presidio State Park that can help manage some of these issues. The first recommendation is establishing cisterns and other water capturing devices. Many of the main buildings on the property are already equipped with gutters and downspouts that could be easily modified to be directed into above-ground cisterns. Several buildings already have concrete pads at the base of the downspouts that would serve as a ready base for large cisterns. These would also be educational opportunities, and diagrammatic and interpretive signage would be to the added benefit to the visitor in the understanding of how these rainwater catchment systems work.
Another recommended strategy is curb cuts, especially in the planting beds in the parking lot. The parking lot and associated entry garden bear the brunt of the stormwater runoff from the village. Added to the impermeable asphalt paving, this creates a large amount of sheet flow that can only be absorbed by the drainage hole at the bottom of the parking lot, near the park entrance, where water tends to gather and pool during storms. The runoff from the streets and parking lot concentrates the surface contaminants at this single point and can possibly affect the quality of the water that runs off into the Santa Cruz River. By creating curb cuts at strategic points in the central planting beds, stormwater can be directed into the beds, contributing irrigation water to the plantings as well as increasing the time of concentration into the ground below. This runoff will help support an increased number of plantings on the parking islands and help redirect surface contaminates into areas of less concentration.
The last major strategy recommendation is grading and drainage. Currently, the site has been largely aligned with existing topography and the drainage creating by the sheet flow both from the village and from the site itself. Creating intentional drainage pathways, interspersed with a series of microbasins to slow the time of concentration and further infiltrate the water into the ground will direct water flows away from buildings, pathways, and other areas where a high flow of water is potentially problematic, and can also create an environment to support dense plantings throughout the site. One such of these areas is the Santa Cruz Interpretive Trail. This trail starts at the main storm drain in the parking lot and directs the water with a series of microbasins along the existing drainageway. This will break up the heavy flow of the water. Planting the microbasins with shade trees and more water demanding species will visually and metaphorically connect the site with the Santa Cruz River that lies just beyond the park’s boundaries. Interpretation alongside the trail can provide explanations of the importance of the Santa Cruz River in the inhabitation and development of the Tubac presidio, as well as the importance of water overall in the upper Sonoran Desert habitat.