Total Maximum Daily Load Implementation Modeling, Planning, and Design: A Synthesis of Resources for Watershed Stakeholders

The ASCE Manual of Practice (MOP) 150, "Total Maximum Daily Load (TMDL) Development and Implementation: Models, Methods, and Resources," was written by the ASCE-EWRI TMDL Analysis and Modeling Task Committee. Chapter 12 of the MOP, "Modeling for Total Maximum Daily Load Implementation," discusses state-of-the-practice on uses of models in TMDL implementation planning. The committee is currently expanding its work. In this paper, an overview of green infrastructure (GI) and modeling of those for TMDL implementation and reviews of specific models, including the USEPA's GI Modeling Toolkit and the Landscape and Green Infrastructure Design (L-GrlD) model for designing GI strategies with flexibility to support stakeholder engagement and decision support tools for stormwater management that can advance the TMDL implementation state-of-the-practice, are presented. Non-traditional approaches are presented with cost-effective implementation while broadening the scope of TMDL to combine with other similar watershed management efforts for greater synergy. Designing of TMDL implementation measures (e.g., BMPs), including engaging stakeholders and managing multiple co-benefits and diverse costs, is discussed as those are crucial steps for the success of TMDLs. Emerging technologies, for example, remote sensing, are discussed with an example from the perspective of efficacy of the implementation measures in the long run.