A buried creek’s dilemma: to be daylighted or drained?

December 28, 2021 § 3 Comments

[Opening digression: I was just texted an image predicting rainfall for LA for the next few days – it looks like you could get hammered (rainfall-wise – what you do with alcohol I have no predictions for), so this post may seem ironic, misplaced, bad timing? You’ve got a trough heading your way and if it doesn’t keep moving…well let’s just hope that it does. The focus of today’s post is dry-weather flows…]


To those of us who recognize stormdrains (or, some of them) as body-snatched creeks, and who long for a water management approach that would incorporate daylighting or naturalization of concreted waterways and nature-based treatment that doubles as streetside landscaping, floodable parks, greenways, etc., well, prepare to be disappointed. Or enraged? Whichever, it’s a familiar feeling. At least we’re not alone on this.

The City of LA recently issued an IS/MND (Initial Study/Mitigated Negative Declaration) and awarded a contract to start work on diverting low flows from certain stormdrains. The low flows – aka urban slobber in some circles – would be pumped from the storm drains into the sewer system, so that they can be treated for pollutants. From there, like the rest of the region’s wastewater, it either gets discharged into flood control channels rivers, is infiltrated to groundwater, or reused (such as purple pipe irrigation). So you can see how it closes some loops and ticks some sustainability boxes.

Especially if you think about water in isolation of the environment… habitat, ecology, and watersheds.

Some of those stormdrains are buried creeks. (You knew I was going to say that) If you look at stormdrain maps (I just spent the better part of the day at the county and city’s websites doing this), you’ll see that our poor little creeks are chopped up not just into multiple threads of city/county/other stormdrains, but that those flows are sent off in multiple directions. Arroyo de las Pasas/Posas, one creek that at first glance appears to be impacted by this proposal, flowed from Lincoln Park and the Selig Zoo once upon a time. As you can see in the image, now the upper portion of its historical drainage flushes out to the LA River down Alhambra Road, while the watershed of its lower half is still directed down closer to the original alignment, but in multiple stormdrains.

Left: historical USGS (1894) with contemporary streets superimposed (freeways most visible). Blue arrows point to Arroyo de las Pasas. Red dashed arrows refer to the map at right. Right: stormdrain map from County website. Blue is County drain, Purple is other drains. Pink outlines show how the stream’s watershed has been chopped up, dashed red lines show the direction and approximate placement of outfalls.

It’s not clear if the low flow diversion project captures a small watershed or the entire lower half of the former creek’s watershed (or is that the creek’s former watershed?).

Left: City of LA map of proposed low flow diversion site. Right: estimated location superimposed on stormdrain map (by me). As you can see it intersects multiple stormdrains (purple and grey lines).

This complicates generalizations about to be made.

The argument behind low flow diversions are rooted in the idea that these stormdrains are not natural, not creeks, and that therefore the flows in them aren’t the base flow of a stream. They’re imported water spilled over from the street. From careless lawn waterers, car washers, gob-spitters or worse. They’re polluted waste.

Back in my watershed coordinator days, I’d taken anyone who’d listen to me (including some agency folks and journalists) to visit springs and watch naturally-occurring not-imported-water trickle into catch basins. I’d even argued within my workplace for creating a study to measure this (and one such study got funded later to a university – I think they concluded 15% was natural in one area. I don’t know how to find that study anymore). It isn’t really known how much of the base flow in our storm drains is “natural” water, but you can bet some of it is. And the persistence of that flow, despite all that has been done to entomb our creeks, to kill them off, is perhaps one of the most hopeful symbols that should be our lodestar forward.

But instead, we lean towards mechanization, again, over nature. The application of the proposed low flow diversion along the former North Branch of the Arroyo Seco1, 2, also known as Arroyo del Cal, has perturbed many.

Screenshot from 1939 storm drain plans entombing Arroyo del Cal aka North Branch of the Arroyo Seco in a culvert. Note the stream’s original name shown on the plans, as well as some trees, including a 42″ sycamore. Elsewhere upstream willows were noted.

The diversion is at the bottom of the stormdrain creek, which in theory would leave water in any upstream reach of the creek that might be able to be daylighted – but then draining a creek, even at its downstream end would probably not be allowed – a disincentive for daylighting. And clearly a diversion above a potential site is inherently a disincentive. Either way, once you’ve got these diversions in place, government’s motivation to daylight the stream becomes even weaker. They’ve certainly not – YET – found public sentiment much of a reason to do it, something I learned rather painfully at the North Branch/Arroyo del Cal, a resistance which others have also bravely sought to overcome.

Left: Cross section showing placement of stormdrain relative to existing channel. (The reason it doesn’t look like a proper circle is that the scale is exaggerated in order to fit more info on the page). Right: Soil boring example, with groundwater (GWS) above the invert of the pipe.

So back to urban slobber vs base flow. In the case of the North Branch, for example, I took a look at the stormdrain plan’s soils borings and cross sections showing where the pipe is placed in relationship to what was presumably the stream’s former channel.

There were 33 borings. Nine of them showed the groundwater either above or within less 3 feet of the invert (bottom) of the culvert pipe. For what it’s worth, I found similar examples of this for both the Arroyo de las Pasas and Arroyo de los Reyes1, 2, 3 (the other piped stream that has a much smaller chopped off area shown as targeted for diversion…I think).

Springs get capped and piped. Groundwater is what feeds the base flow of creeks. We see sources of baseflow in these old borings. I admit I do not fully understand, beyond the capped/piped springs that I’ve seen, the mode of entry for all this water into supposedly watertight pipes. But there is also chemical evidence of “natural” water in some stormdrains. The important point here is that these diversion projects are not necessarily diverting only “urban slobber” – yet to do so nails the coffin on our creeks.

To be fair, the City is in a bind – their ISMND says they have to be bacteria-free by 2023. (The 2010 TMDL says they have 15 1/2 years but I’m sure there been a few pounds’ worth of reports and correspondence and studies in the intervening years of those two documents that explain the discrepancy). And there’s genuinely good people behind this report, probably doing the best they can within constraints we don’t fully understand, but probably have something to do with work silos and internal politics.

But at the risk of redundancy, the solution reinforces the hyper engineered modus operandi of LA towards the environment. We nip and tuck at nature like a sadistic plastic surgeon. It’s a microcosm of an attitude that has been applied to varying extents all over the world. And the world – the natural one – is pushed to the point of calling out our hubris in the form of killer storms, killer fire, killer winds, killer heat…

What would have taken a lot more coordination but maybe would have had more ecologically-driven multi-objective/multi-benefit um…benefit, would be, for example, city-wide streetside rain gardens and bioswales, or as The River Project dubbed it back in…2009(?) “urban acupuncture” as they kicked off a project called WaterLA. It would have required different departments at the City to play together, breaking down old paradigms of managing public space, and to maybe even enlist legions of residents and people in need of jobs to implement these projects. Clean up the contamination as close to the sources as possible, get some good urban greening – and restore the streams where you can. The ideas have been around for a while. I’ve personally heard variations of them since 2001. And so have a lot of the people making decisions on this stuff.

It would indeed take some heavy lifting. The kind that will be needed, by the way, to truly prepare for (seeing as we also haven’t already lifted heavily to mitigate) climate change. In other words, if LA really wants to live up to all its sustainability bravado it’s probably going to have to bust through some ossified ways of doing business and re-structure, re-mission and revisit a lot of decisions that have sacrificed good design, nature and public space at great public expense. There’s not time to dither on this. Consider more integrated and restoration-forward solutions for these humble streams your warm up exercise. Work out the kinks on Arroyo del Cal. (If it feels like I’m singling out the City of LA, a certain County proposal to put big concrete platforms over the LA River isn’t out of my sights, it’s just a monster to read and think about).

I’d also like to suggest to the regulatory/legislative community that you start to treat our former waterways like… well, waterways-that-should-be. Can’t say the “no net loss” policy of environmental laws has resulted in equivalent quality of wetlands and waterways, and I do somewhat doubt that it has resulted in no net loss. So it’s past time to create regulatory priorities for recuperating what has been lost, and protecting in a meaningful way what remains. And having some consistency with this statewide would be nice too. Dare I say, nationally?

So what’s a cranky creekfreak to do? We’re in this together. Tim Brick at the Arroyo Seco Foundation is leading the fight – in fact his advocacy has alerted the Eastsider who wrote a great piece about this, and the Arroyo Seco Neighborhood Council, which has written a letter to the City expressing concerns. Check out the ASF webpage. Sign their petition and crank freely in its comments sections (feel free to crank here too, but it will have more impact over there). And if you live in the City of LA call your council reps. If you want to see state policies change, call your assembly and state senate members. If you want national policies to change, call your congressional reps and US senators. And while our regulatory agencies are really just implementing existing laws (and reacting to lawsuits resulting from incomplete implementation) – implementation can prioritize different approaches. The leadership needs to know you want them to care about your neighborhood buried creek.

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