Restoring Malibu Lagoon
September 26, 2010 § 43 Comments
Back when I was involved in native planting projects and miniparks along the rights-of-way of flood control channels, I sometimes worried that people would get too attached to those things – to the extent that they’d not support restoration of the channels if it meant losing their minipark (any restoration would require us to widen the channel within the right-of-way). Would people object to bulldozing a created upland habitat to re-establish riparian habitat? That may seem like an overblown fear, but I see that reflected from time to time in environmental debates. There are good reasons for keeping some things the way they are, but sometimes there are also important reasons to make changes. The currrent reflection of that for me is at the Malibu Lagoon.
Disclosure: I’m not involved and haven’t been involved in the design or any decisions on the lagoon, but I am preparing a drawing of it for the project proponents. And between getting informed on the design and seeing some of the opposition rising, I decided to post my understanding of the issue – no one asked me to do this. Thanks to Mark Abramson for taking the time to describe some of the project history and the proposal.
The lagoon as we know it was created in 1983. It was a vast improvement over the ballfields – and the dump (from the 1930s-60s) – that had previously replaced the natural coastal wetland there. Malibu Creek drains to the lagoon – you can see a wide open area where these flows come in in the photo above. And to the left are tidal channels, looking like curly little fingers. These were created by a bulldozer, cut fairly steeply by its bucket, which limits the diversity of habitats along a salt marshes’ tidal prism. So creating shallower slopes would increase the diversity of habitat. Also, optimal tidal flushing is limited by the circulation of the channels and perhaps more significantly, by the boardwalk that bisects them. Encroaching mounded soil and boardwalk piers constrain the ability of water and sediment to move through. Over the years, fine sediments have accumulated (natural occurrence at a wetland) but have not been able to flush out.
Speaking of flushing, as we all know from the news, lots of folks in Malibu flush their toilets into leaky or ill-placed septic systems, resulting in high bacteria counts at Surfrider Beach. It and other discharges into Malibu Creek also contribute to high nutrient levels. Excess nutrients (fertilizers, poop etc) wreak havoc on a system. (This week’s LA Times pieces on sea otters and Calabasas septics dramas provide insight into the range of havoc that ignoring its effects can wreak-biological and political/personal.) If you’ve owned fish and never changed the water and didn’t have an aerator, you’ve seen the issue in a microcosm: nutrients cause an explosion in growth of plant life, which then dies and decomposes – consuming the water’s oxygen in the process – and little Charlie and BigMama are suddenly floating upside down. It’s not pretty when it’s in your tank, and it’s worse when it’s a river, lake or wetland. Mark Abramson said he’s been called by residents five or six times over significant fish die-offs in the Malibu Lagoon over the years.
Which brings us back to these fine-sediment choked, non-flushing tidal channels. With the high nutrient levels coming in from Malibu Creek and adjacent septic systems, the nutrients are binding to the wetland sediments, stored as reserves – and not flushing out (long term thought – and what happens when it flushes to the sea – which is why we really need to rein in the fertilizers and figure out better ways to deal with waste). Instead, the nutrients periodically get re-released into the water column, bringing us back to fish kills and diminished wetland habitat. So to me it makes sense to redesign this area to restore natural levels of flushing (the seasonal quality of the lagoon’s breaching of the sand berm remains). It can’t be a cure-all for the wastewater problem, but it restores natural function within its boundaries, which will help the overall health of the lagoon.
To do this, the restoration project creates better tidal circulation with new channels that have shallower slopes. It also removes the constricting boardwalk, relocating it to the outer edge of the wetland. This not only frees up tidal flushing, it also creates a deeper interior for habitat – you may have noticed, wildlife don’t always like us in the middle of their business. For some reason, we often seem predatory and threatening. So moving us to the outer edge gives them more room to feel secure. But we will still get to watch them from behind bird blinds and overlooks.
Finally, the parking lot in the restoration plan is moved closer to PCH – already built – and detaining and treating stormwater runoff. Moving it adds 2 acres of habitat to the wetland.
Mark tells me there will be a biologist on site throughout the project, no poisons will be used, and hand-digging will be done in areas expected to be culturally sensitive.
Such work impacts habitat temporarily – and after 27 years of establishment, it may seem unwise and callous to disrupt it. But the boardwalk and contaminated sediments are a permanent disruption that diminishes habitat quality that the lagoon will not recover from without action. These restoration decisions improve the natural function of the wetland and should benefit fish, bivalves (clams, mussels) and benthic invertebrates – all of which should benefit the already plentiful birds there even more. I’m excited about it, and see this as the next step, as we understand and refine our knowledge of wetland and fluvial systems, we get better and better at restoration. Getting rid of constrictions is one of the most important things we can do to let natural systems repair themselves – creating new tidal channels based on the geometries of channels in healthier wetlands gives the lagoon a boost in its recovery process.