The Downtown Greenspace Plan

Our team is happy to present the final report of this project, the Downtown Greenspace Plan. This plan is the culmination of 9 months dedicated to preparing a data-driven, public-focused plan to ensure the viability of future downtown greenspace. To view the plan, please click the below.


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Urban Heat Island – The Effect of Imperviousness

The urban heat island (UHI) effect describes built up areas that are hotter than nearby rural areas. Large amounts of paved surfaces in urban areas absorb and retain solar radiation at a much greater rate than natural areas with exposed vegetation or soil. The result is the release of warmer air at the ground level. Another factor that contributes to warmer ground temperatures includes the inability of urban areas to absorb and naturally infiltrate rainwater, which means less moisture in the soil making the evapotranspiration process less intense. These processes are graphically depicted in the image shown below.


As part of our team’s assessment of downtown Sioux City, we created a unique dynamic systems model to predict the urban heat island effect as a result of the high imperviousness of downtown. The model was created in a systems modeling program called STELLA, and can predict local temperatures for any geography with local inputs for land cover units like roads, buildings, grassland, and trees.

Based on our model, we predicted the UHI effect in Sioux City is 4.53°C warmer than nearby rural areas. This prediction does hold true, within about 1 degree Celsius margin of error, when examining historical temperature trends. 

Several additional degrees of heat does play a significant role in many factors of everyday life downtown. Some of these effects include hotter air temperatures in urban areas compared to adjacent rural areas, hotter surface temperatures, higher energy use, building and stormwater maintenance costs, sunlight-related health problems and air pollution. In addition, they have an adverse effect on wildlife habitat and plant growth in urban areas.

Our main goal when modeling the UHI effect in Sioux City was not simply to predict the magnitude of the problem, but also to present methods for reducing the additional heat. Our team came up with 4 scenarios, some of which closely resemble the recommendations that will be detailed in the final Downtown Greenspace Plan: (1) increase street trees, (2) convert several public surface parking lots into greenspace, (3) re-paint rooftops in white, light-reflecting paint, and (4) all the previous scenarios combined. After localizing the model with new inputs for each scenario, the resulting UHI magnitudes are displayed below.

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As expected, the combined scenario produced the largest reduction in the UHI effect. Both the white-roofs and street trees provided additional reductions as well. The positive UHI change of 0.04 degrees Celsius is negligible. However, this may speak to the need to increase tree coverage on grassland parks in order to provide additional shade and cooling factors. The graph below shows these scenarios played out over the course of one day, with the blue line representing nearby rural temperatures. Here, a clear summer day in June is assumed.

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As the results show, significant reductions in the UHI effect in downtown Sioux City will take significant investment in greenscaping as well as other less conventional means like white roofs, green roofs, cool pavement, and other building materials that properly reflect,  absorb, and emit the sun’s solar radiation. In the near future, the development of the Pearl Street Park in downtown will certainly become a refuge for escaping the surrounding heat.

Updated Greenspace Designs and Open House Results

The following posters were presented on Saturday at our public Open House in order to showcase several greenspace designs and their various amenities. Many of the renderings shown on the posters are updates from February 5th’s post. Click through the slideshow to see the posters and renderings!

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Participants voted on various design amenities using a provided set of stickers. The results of the voting on these amenities have been tabulated and are presented as follows:


Out of all of the concepts or amenities that were presented, the green roof concept on top of the Discovery Parking Ramp received the single highest number of stickers. Other highly regarded amenities included constructing a pond with a bridge in the Children’s Museum pocket park as well as incorporating native prairie landscaping and diverse tree species throughout downtown. These results will be provided to city leaders and other decision makers to guide future greenspace design decisions.


Pocket Park Drawings

We want to thank everyone who participated in drawing their “Dream Pocket Park” while at the Open House on Saturday. We will also soon be posting the results of the voting process for the 6 greenspace designs that were presented in the lobby of the museum. Look for your own design below!

Community Open House

On Saturday March 5th from 12-3pm, the Downtown Sioux City Greenspace Plan project team, will hold a Community Open House event All Sioux City residents and employees are invited! Please join us in the lobby of the Sioux City Public Museum to discuss the future of greenspace for downtown Sioux City. Refreshments will be provided.

Who is the Downtown Sioux City Greenspace Plan project team?

Ben, Katie, Parker, and Varsha are Urban and Regional Planning students at the University of Iowa in Iowa City, IA. Throughout the course of this school year they have been working in partnership with the City of Sioux City, the Sioux City Downtown Partners Association, and the Siouxland Interstate Metropolitan Planning Council, to create a greenspace plan for downtown Sioux City.

Why should you care about greenspace in Downtown Sioux City?

Improved greenspace in downtown Sioux City, IA creates a more beautiful, sustainable, and recreational environment for all downtown residents, employees, local, and non-local visitors. It can help reduce local flood risk, water pollution, and air pollution. It increases the quality of life for everyone.

At the open house:

  • You will get chance to vote on your favorite greenspace amenities for downtown Sioux City, and suggest additional amenities;
  • Kids and adults will get to design and draw their own parks and greenspaces;
  • You will learn about the purpose, goals, and vision for the Greenspace Plan currently being developed for downtown Sioux City;
  • You will be able to communicate your ideas for downtown greenspace to Ben, Katie, Parker, and Varsha (authors of  greenspace plan);
  • You will learn about greenspace plans completed in other cities;
  • You will learn how a wide variety of greenspace components, amenities, and designs can contribute to the social, economic, and environmental improvement of the downtown Sioux City urban environment;
  • **Ragen Cote, the Executive Director of Downtown Partners, will show active design plans and gather public input for an upcoming parklet project for Pierce and Nebraska Streets in downtown Sioux City. This project would reduce three lanes of one-way traffic to two lanes to allow for diagonal parking along the right hand side of the street and greenspaces (parklets) on each corner. There would be 16 parklets and 104 additional parking spaces added for visitors on Pierce Street (3rd – 8th Streets) and on Nebraska Street (3rd – 6th Streets).

If you can’t come to the open house…

We still want to hear from you!

Click on the following link for a template to draw your greenspace: Draw Your Own Greenspace. Please email your greenspace artwork and any questions, concerns, policy suggestions, or greenspace plan ideas to Or, you can call Sioux City Downtown Partners at 712-252-0014 and ask them to pass your message along to the Greenspace Plan project team.

Please help us spread the word!

Please click on the following link to download a copy of our Open House flier: Open House Flier. If you are able to post this in your place of employment or business, we would greatly appreciate it.

Open House Flier


The Preliminary Design Process

In the past few weeks, our team has been looking into design solutions for specific sites for proposed greenspace. In addition, we have been examining streetscaping options in order to create a network of greenspace that is friendly to pedestrians and bicyclists as well as cars. These solutions are intended to accomplish as many of our social, environmental, and economic objectives as possible. Our map of project greenspaces specific for our plan is shown below. While it isn’t an all-inclusive list of all areas where greenspace may be implemented in downtown Sioux City, it serves as a good starting point for our team to move forward with site specific greenspace solutions.


The following are preliminary designs for some of these spaces:


Bioswale along Sixth Street towards intersection with Nebraska. Designed with native prairie plants in order to increase stormwater infiltration as well as reduce surface runoff, as well as to provide aesthetic benefits, improve soil quality and increase plant biodiversity in downtown.

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A pair of alternatives for the alley between the United Center and Promenade Theatre. Designed to provide a place for residents in the United Center as well as the public to congregate as well as to improve aesthetics, biodiversity, and economic value of adjacent properties.

Green buffer area along Perry Creek. Designed to improve aesthetics around the stream as well as to improve plant diversity, filter stormwater pollutants prior to reaching the creek, improve bank stability, and provide trail users with an improved experience.

The designs presented above as well as designs for additional sites will be shown to the public in an open house forum in order to gauge preference for alternatives presented at each site as well as to gather input on additional amenities that the public might want in these spaces.