Weed management in flood control facilities is important to maintain water flow and protect infrastructure. There are various types of weeds including emergent, terrestrial, and floating weeds that require different control tools. Regulatory constraints include NPDES permits that limit chemical use and injunctions protecting habitats. A 2003 cost and water quality study compared manual, mechanical, chemical, and goat grazing techniques, measuring control costs and water quality impacts. It found that while mechanical techniques were expensive and required annual use, goat grazing worked well with minimal water quality impacts. Using chemicals followed by mechanical methods was the most cost effective approach with minimal risk to aquatic environments from pesticides.