Citation:

Massoudieh, A., M. Maghrebi, B. Kamrani, C. Nietch, M. Tryby, S. Aflaki, AND S. Panguluri. A Flexible Modeling Framework For Hydraulic and Water Quality Performance Assessment of Stormwater Green Infrastructure. ENVIRONMENTAL MODELLING AND SOFTWARE. Elsevier Science Ltd, New York, NY, 92(C):57-73, (2017). https://doi.org/10.1016/j.envsoft.2017.02.013

Impact/Purpose:

A new green infrastructure modeling tool was developed. Before this there were no commonly used tools to aid consulting engineers and researchers in simulating green infrastructures for stormwater management. This new tool, called the Green Infrastructure Flexible Model (GIFMod), is free to download and can be used to simulate a variety of different practices. GIFMod will most likely be used by stormwater management design engineers or researchers interested in understanding how green infrastructure design impacts performance for both water quantity and water quality. The model can be used by consulting engineers hired by local communities to manage stormwater runoff for compliance with National Pollution Discharge Elimination permits, and also by communities, engineers, planners and regulators.

Description:

A flexible framework has been created for modeling multi-dimensional hydrological and water quality processes within stormwater green infrastructures (GIs). The framework models a GI system using a set of blocks (spatial features) and connectors (interfaces) representing different functional components of a GI. The blocks are used to represent spatial features with the ability to store water (e.g., pond, soil, benthic sediments, manhole, and a storage zone) and water quality constituents including reactive chemical constituents and multiple classes of particles. The connectors represent the flow and mass transfer between each pair of blocks. Each block and connector, depending on their identity, can be assigned different constitutive relationships controlling the head-storage (H-S) and flow-head (Q-H) relationship, respectively. The computational engine of this flexible model solves equations describing critical mechanisms related to GI model performance that can be grouped into three categories: 1) hydraulics, 2) particle fate and transport, and 3) coupled dissolved and particle-associated reactive transport of water quality constituents (e.g., pollutants). Regarding the hydraulics, the model can solve a combination of Richards equation, kinematic/diffusive wave, Darcy, and other user-provided flow models simultaneously. The particle transport model is based on performing mass-balance on particles in different phases, e.g., mobile and deposited in soil with constitutive theories controlling their transport, settling, deposition, and release. The reactive transport modules allow constituents to be in dissolved, sorbed or bound to particles, and also to undergo user-defined transformations. The numerical solution is based on an adaptive time-step implicit Newton-Raphson method. A graphical user interface (GUI) has also been developed that allows users to visualize the conceptual layout of the GI system being modeled as well as define and parameterize the transport and fate mechanisms. Four applications of the modeling framework are presented that demonstrate its flexibility for simulating the performance of common urban GI types, but each with unique implementation or modeling objectives: 1) the hydraulic processes within a serial rain garden system, 2) a porous pavement system, 3) the hydraulic, carbon/nitrogen transport and transformation, and coupled dissolved/colloid-associated transport of zinc underneath a hypothetical infiltration basin and 4) carbon/nitrogen cycling in a wet pond.

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