Project Statement

“Before the City, there was the Sand” explores the issue of urban flooding in the southern Chicago region through a deep reading of its geological history. The soils and surficial sediments—the sands in particular—are an important part of the hydro-geologic and geographic history of the Great Lakes region. This project calls for a “re-surfacing" of the sands in the spatial and infrastructural design of the urban landscape relative to water and stormwater management.

In this geological context, the project specifically explores the material origins of a 300-acre neighborhood in Calumet City, IL. The site and community are located within greater industrial Chicago and adjacent to one of the ecologically richest dune regions in the southern Great Lakes region. Our interdisciplinary team of landscape architecture, geology, and civil & environmental engineering students used soil studies, modeling, and design to reveal patterns of the geological legacy of beach ridges and dune-swale ecology. We used these patterns as functional intermediaries for rainfall, but more importantly, as ways to construct new relationships of people with a forgotten landscape.

Project Narrative

Riffing on the opening line of Nature’s Metropolis, we call this project “Before the City, there was the Sand” (Cronon, 1992). Cronon describes the source of Chicago’s urban and economic development through the exploitation of its regional landscape, whereas we reclaim the lost landscape, specifically Chicago’s geological history, in an effort to reimagine its future. Over time, sands have been mined for site construction and dunes have been entirely leveled for urban development. With the exception of a few remnant nature preserves, the surficial expression of coastal sands, ancestral dunes, and beach ridges (remnants from Lake Michigan’s former shorelines)—have mainly been erased, altered, or paved over.

The consequences of this geologic site erasure have been borne by communities and the waterways of the region. Soils that would have infiltrated water have been paved over, and the gray infrastructure system that bypasses soil infiltration has fundamentally altered hydrologic flow in the region. The gray infrastructure is now under capacity relative to urban development, creating blockages in the system and flooding in streets and basements. Communities in Calumet City’s low-lying areas with inadequate infrastructure suffer the worst. Our project takes a closer look at the issue of urban flooding in order to propose solutions in and on the land--at a material, formal, and social level.

Our team is composed of students from landscape architecture, geology, and civil & environmental engineering. Together we conducted fieldwork on surficial soils of the region, modeled those soils for their role in green stormwater infrastructure design, and developed a design strategy for the northwest neighborhood of Calumet City. The 300-acre neighborhood sits in a low-lying area of land just inside the ancient Toleston beach ridge that extends northwest-southeast, parallel with the current shoreline of Lake Michigan. The site experiences severe and frequent flooding. Further, the existing neighborhood sewer system is under capacity, and due to low slopes, is unable to convey water to the large central detention pond located to the north of the site.

Our approach to these entangled issues was to study the site’s geological history, material nature, and topological condition in order to shift the perception of water from a problem to an amenity for people in the neighborhood. We proposed to create places for water that ameliorate the pattern of street and basement flooding through a new pattern of green infrastructure inspired and informed by the distribution of sandy sediments underneath the city.

In summer of 2018, our geology and landscape architecture students conducted fieldwork to investigate the soils in the area. We wanted to discover what soils exist here and how they play a role in rainwater infiltration. We were trained by Quaternary geologists from the Illinois State Geological Survey and soil scientists from the Natural Resources Conservation Service on how to take soil cores and to use Amoozemeters, an instrument that measures Ksat (saturated hydraulic conductivity). We characterized soils on site and analyzed grain size distributions in the lab in our University. The soils of Calumet City are beautiful—much of the near-surface materials consists of loamy fine sand to loose beach sand, typical of the coastal region. A few localized areas of peat occur in depressional areas and finer-grained sediments occur on the plains of glacial Lake Chicago, southwest of the beach ridge. The beach ridge sands were sourced from older glacial sediments and then transported with shoreline processes as the Lake Michigan’s coast retreated over the last few millennia. Sands there have high infiltration capacity, and when layered beneath green infrastructure—for both planted and paved upper surface designs--promote direct infiltration.

We created small prototypes for how substrate sandy soils and green infrastructure would perform and tested them across hypothetical “loading ratios” for the site (defined as the surface area of run-off to green infrastructure). Our interventions to transform the existing condition of pavements and compacted soils across the neighborhood “tap into” the soils below. An understanding of the characteristics and the modeled performance of the soils provided excellent knowledge from which to then imagine the design intervention.

When we visited the Calumet City neighborhood site in Winter of 2018-19, we observed the rigid pattern of the street grid that belied its underlying geologic pattern. We visited regional nature preserves to study the landscape surface--the dune and swale landscape type--and wondered how to recall, reveal, and creatively reimagine the regional landscape in such a highly urbanized condition. We did not desire to mimic this landscape but instead, to find new relationships for people of the community with this forgotten landscape.

The metaphor and imagination of these hidden systems of land and sand filtered into our analysis--we overlaid contrasting systems and learned to read the essential nature of the site. We mapped across scales—from soils to site systems—and found a creative approach to forge new relationships. With the patterns of the region’s ridges and dune-swale geological origins in mind, we studied the topography of low and high areas in the neighborhood as an emerging relationship between wet and dry areas in the design. We used planting to signify geological patterns--with color and texture schemes for high-dune areas and low-swale areas. Together the topographic and planting coordination speaks to the hybridity of urban and geologic patterns, an approach to the complexity of hydrology and human spaces that now occupy the land.

Key to engaging the soils and the hydrological surface interface was to develop a matrix of designed surface types--from turf stone pavement to landform design. We established a gradient of rain capacity based on the site and surface type from wet to mesic to dry. We want these strategies to provide options to communities to envision a transformation of the surfaces of streets, public ways, and park and schools in the process of integrating new designs.

Our primary areas of design intervention were the streets, with a predominance of “wet streets” that frequently flood, but that are now designed to infiltrate a lot of water. We also proposed designs for three site types in the community--a public park, a commercial parking lot, and a public school. Although the typologies of each site differed, we introduced a regional aesthetic of landform surface design that integrated a shared palette of spatial experience and planting. Landforms provide subtle clues to the geological history of the site. Dunes and playmounds become exploration and lookout spaces for children at school and in the neighborhood, while using these landforms to conduct water flow to low areas for collection and infiltration. The plant palette contains species predominantly native to the region; as the plants knit a root system together and nourish the soil, the surface becomes a sponge that processes rain through plant evapotranspiration. Once the upper soil is saturated, water infiltrates below into the substrate sands.

Key to helping the Calumet City community and Chicago make decisions for green stormwater infrastructure was showing how it works. We modeled the design for the neighborhood using the open-source software EPA-SWMM. The model accounts for variability of surface design interventions (thickness and depth) to simulate runoff reduction performance with the site’s native soils in response to changes in rainfall intensity (volume over time). The outputs from this model allowed the communities to see how reliable the proposed intervention will be under different soil and climate conditions, and how simple design changes can be used to improve that reliability. We then used the overland flow modeling software MIKE 21 in order to identify areas that are vulnerable to flooding. Using the outputs from EPA-SWMM analysis, we then back-calculated the maximum storm for which the design interventions were 100% reliable in reducing runoff. This analysis allowed us to identify catchment areas for further private green space intervention. Finally, a catchment-based runoff reduction methodology was implemented within MIKE 21 to identify how much the proposed design interventions reduce surface flooding.

Cronon, William. (1992). Nature's Metropolis: Chicago And The Great West. New York: W.W. Norton. The opening line of Chapter One reads “Before the city, there was the land.”