Balancing Preservation with Landscape Performance: JBC's Work at Terrace Hill

JBC served as the lead landscape architect and consultant for the Terrace Hill Erosion Control project, addressing significant stormwater and erosion issues on the grounds of the historic Governor’s mansion in Des Moines. Working with the Iowa Department of Natural Resources (IDNR) to establish key stormwater management parameters, JBC developed a site-sensitive design that resolved active erosion problems while maintaining the historic integrity of this high-profile property.

Prior to the project, uncontrolled stormwater from downspout leaders was flowing freely across the landscape, creating visible erosion and degrading the site. JBC designed two bioretention basins (rain gardens) to capture and infiltrate this runoff, allowing water to filter into the ground while reducing the volume and velocity of flow across the property. These basins were carefully sized in coordination with IDNR to ensure proper function based on the watershed area and typical storm events.

To manage larger storm events, JBC included an overflow system that connects to the site’s existing stormwater infrastructure. A series of weir walls within the rain garden areas act as check dams and create a mini "treatment train” that slows, filters, and detains stormwater, turning a formerly problematic zone into a functional landscape feature that supports water quality.

Designing within a historic site required a careful and respectful approach. JBC strategically located BMP stormwater features to preserve key viewsheds and avoid disrupting the character-defining features of the estate. Existing infrastructure posed additional challenges due to its age and limited documentation, but thoughtful coordination and innovative design by the JBC team helped overcome those constraints.

The project proved its success quickly. JBC observed the first rainfall after installation and confirmed that the new systems performed as intended, mitigating erosion and managing flow. The Terrace Hill erosion control project is a strong example of how sensitive design solutions can address modern environmental challenges while respecting the context of historically significant landscapes.