The Green Infrastructure Flexible Model (GIFMod) is an open-source framework for modeling urban stormwater and agricultural green infrastructure (GIs) practices. GI practice refers to a decentralized network of site-specific stormwater management techniques implemented to reduce the volume of stormwater runoff entering the sewer or the receiving stream and potentially improving the overall water quality. Some examples of GI techniques include:
- Cisterns/Rain Barrels,
- Vegetated (“Green”) Roofs,
- Infiltration Practices (Basins, Trenches, Dry Wells),
- Pervious Pavement with Infiltration, and
- Vegetated Swales
GIFMod allows users to build conceptual models of these aforementioned or other similar GI practices to predict their hydraulic and water quality performance under given weather scenarios. It also allows for interpreting the field and lab data collected by the researchers via its deterministic and probabilistic inverse modeling capabilities.
In GIFMod, models of various GIs are built as a combination of blocks representing different media types including surface water, streams, overland flow, saturated and unsaturated porous media, and storage volumes.
GIFMod provides the users the ability to consider the following physical-chemical processes when modeling GI performance:
WATER QUANTITY PROCESSES
- Evapotranspiration and vapor flux
- Flow through pipes and weirs
- Overland flow
- Stream flow
WATER QUALITY PROCESSES
- User defined chemical and biochemical transformation
- Solid-water mass exchange
- Particle/colloid fate and transport
- Particle/colloid-associated transport
- Plant uptake
- Contaminant build-up on surfaces
- GIFMod allows a user the versatility to model hydraulic and fate and transport of contaminants in systems composed of multiple types of media governed by different governing equations.
- GIFMod gives the user full flexibility in terms of including or excluding various processes while defining the model setup.
- The reaction network or equations affecting the transformation of contaminants can be designed entirely by the user.
- GIFMod uses an adaptive time-step numerical approach that reduces the computational speed and increases the stability of the numerical method compared to fixed time-step methods.
- Unlike other models, GIFMod can handle “abnormal” situations when blocks become completely dry which makes it suitable for application to GIs when a complete dry situation is a common occurrence.
- The deterministic and probabilistic inverse modeling ability makes GIFMod a good candidate for hypothesis testing and evaluation of the significance of various processes potentially affecting the performance GIs.