Stormwater Modeling: It Can Be Done, and You Can Do It

Why Model?

As a site designer, planner, or environmental manager, you can create a representation or simulation of a site and apply various environmental data to determine possible impacts. You’ll need this data to determine whether you’ll meet mandatory or voluntary performance standards, as well as to assess how various green infrastructure practices reduce flow and pollution from the site. With cost-data in hand, you’ll be able to compare long-term costs and benefits of various “green” and “grey” alternatives, and combinations of the two.

Choosing Another Model

A variety of models are available for assessing the performance of green infrastructure practices in the urban environment, including i-Tree Hydro. But, before you select a model, identify your needs and the resources at your disposal. Check out this annotated collection of tools prepared by the Chicago Metropolitan Planning authority.

Define Your Objective

No model can accurately predict all environmental outcomes at all scales, but most models can predict a limited range of environmental outcomes within a limited range of scales. Identify:

  • Environmental parameters you want to include in your model (e.g. water quality, streamflow rates, groundwater recharge rates); and
  • The scale you want to simulate (e.g. a single site, a small headwater stream, a large lake).

i-Tree Landscape Can Get You Started

You don’t need to be a GIS specialist or an engineer. With a few simple clicks, i-Tree Landscape can estimate the stormwater benefits of trees right on the web. Having this data at your fingertips can help convince stormwater managers to continue the journey.

Determine Your Data Requirements

Simpler models require less data that might be retrieved from publicly-available databases, while more complex models require more data to provide the necessary parameters and calibration. For each model you are considering, determine:

  • The amount of data it requires; and
  • The spatial and temporal resolution it requires.

Choose the Simplest Model That Can Meet Your Objective

Think about the level of accuracy that is required to meet your objective. Efficiently allocate staff and budget resources by weighing a simple model’s level of accuracy and cost against increasingly those of more sophisticated models. Is the incremental gain in accuracy of a particular model worth the incremental increase in cost? Make certain to consider i-Tree Hydro. It’s free and preloaded with much of the data you’ll need.