Here's an example of remediation and turning around open space that is currently not being used in a sustainable way. This strategy by Save LA River Open Space conceives reworking a Studio City golf course into wetlands parkland adjacent to the LA River. This is a long slog, as community orgs such as North East Trees has discovered in its attempts to capture water and retain it near the river, such as is done at the Oros Street project adjacent to the Glendale Narrows portion of the LA River.
The community participation is a crucial factor in getting these kinds of projects to come together, as well as the financing from many sources that require significant cooperation and teamwork. It requires not only design and engineering, but also an ability to implement the construction of these kinds of wetlands and water swales so that they work with the local ecology and the Los Angeles River itself, not to mention the myriad City and County regulations that must be satisfied in these situations. In a watershed, many important public policy and water regulation structures must be dealt with. This can be a very long process that is difficult to fund.