Mayor Garcetti is in Washington DC this week, pushing local infrastructure initiatives like the Regional Connector and Westside Subway. I’m a huge fan of both of those projects, but his biggest priority seems to be lobbying for the most expensive option for LA River rehab. Putting this project at the top of the list is a mistake on both the local and the national level.
At the local level, Regional Connector and Westside Subway will offer a much bigger return on investment. The former will eliminate operating inefficiencies and greatly improve the connectivity of the LRT network. The latter will cut the peak period travel time between UCLA and downtown LA in half. Given that the 10, the 405, and the 110 are among the nation’s most congested freeways, these projects are critical to economic growth in LA County, which is still suffering from very high unemployment. On the other hand, LA River improvements offer tangible recreation benefits, and maybe some tourist benefits, but the economic benefits are largely speculative. From Malibu to Mount Baldy, it’s not like LA County is short on places of natural beauty.
At the national level, the federal agency charged with responsibility for the LA River is the Army Corps of Engineers (ACOE), which for historical reasons is responsible for flood control. ACOE has a huge backlog of projects that are much more important than a trophy park for Los Angeles. For example, port channels need to be dredged, river levees need to be reinforced, and ill-conceived projects that are ruining valuable ecosystems like the Everglades need to be rectified. It is irresponsible for ACOE to spend billions on a park for LA with these needs outstanding.
For an example close to home, consider the Isabella Dam, which impounds the Kern River in the Sierra Nevada above Bakersfield. The dam has seepage issues and was unknowingly constructed on a dormant seismic fault. This has reduced the volume of water that can safely be stored by the dam, which means that a smaller flood could overwhelm the dam. If the dam fails, parts of Bakersfield will be devastated by flooding. To me, it is practically immoral to spend ACOE money on a park in LA while that sword of Damocles is hanging up above Kern Canyon.
Really, there is no federal concern in an LA River park. If we want to build it, we ought to raise the money locally, and have an honest debate about the trade-offs between the park and other potential public investments.
Let's Go LA 
You seem to be leaving out the environmental benefits of the LA River restoration plan. One of the major claims throughout the ACOE documentation is that western North American riparian habitat is one of the most devastated kinds of habitat in the nation. Most of these rivers have either been dammed or settled, and there just aren’t very many of them.
Additionally, this particular project increases the ability to create wildlife corridors connecting Griffith Park to other habitat islands in the area, including the Verdugo Mountains, and potentially the Angeles National Forest at some point when a bit more of the Arroyo Seco is restored.
I tend to think that the park aspects of the plan are overplayed – in fact, human access to a few of the current park areas in the lower reaches of the plan will probably be decreased under Alternative 20, because more of the land area will be converted to wetlands and other habitat. But it seems to me that just as future cities will have to be more integrated with their public transportation systems, I suspect they will also have to be more integrated with their ecosystems, both for the sake of local water resources, and to make sure the ecosystems of our regions continue to function rather than gradually fading away, as they are dissected by agriculture and cities.
Now, it’s definitely not clear how large the environmental benefits of this specific project will be. And it’s definitely clear that the two rail projects that you mention will have huge social and economic benefits for the city and the region. But in the grand scheme of the federal budget, appropriating a billion dollars for this plan could be a very good investment, assuming that this funding is taken from some of the many other federal projects that are much less future-oriented.
That’s true, I shouldn’t sell those benefits short. As the LA Times noted, it’s not so much restoring habitat as it is creating new habitat. Summer flows today are higher than they were naturally, due to discharge of treated wastewater, and winter flows are lower due to the need for flood control. But increasing vegetation and wetland areas is good for wildlife, and reduces the urban heat island effect, which is definitely a positive.