Opportunity knocks at Compton Creek

July 11, 2010 § 3 Comments

Public officials on Compton Creek last week. Photo: Mia Lehrer.

Last Wednesday’s press conference on Compton Creek with EPA official Lisa Jackson has been the source of much navigability excitement in the creekfreak blogosphere, but as Joe mentioned, the press conference had another purpose: to bring together officialdom to celebrate and unite in purpose around acquisition of part of Compton Creek.

If you think the navigability issue on LA’s waterways is tricky, you should take a look at ownership! Blake Gumprecht covers this issue as it related to the LA River in his book, The Los Angeles River: its life, death, and possible rebirth.  Back when the land was being subdivided, there was no zoning set-aside around these waterways. This had the unhappy result of property owners buying and building in some pretty active floodplains – you can guess the results. To this day, if you do a property search on the LA County Tax Assessor’s website, you’ll see that the creeks and rivers of LA that have been converted to flood control channels are noted as either easements over private property, or are now separate properties owned by the government. Reviewing old newspapers about this subject reveals that there was a lot of wrangling (lawsuits) to even acquire those lands, despite the anger and fear around flooding. Public lack of cooperation probably played into the “single purpose” solution we know of today as the flood control system – more land for streams with floodplains would have cost more money and been harder to justify to a public bent on development.

Assessor's map shows Compton Creek as a flood control easement.

So Wednesday brought us a formal announcement that the Santa Monica Mountains Conservancy/Mountains Recreation Conservation Authority acquired 4 acres of Compton Creek’s river bottom from the Crystal Casino; a bike path extension is in the creek’s future and then this land will eventually be transferred to another public entity. The purchase protects this part of Compton Creek from any future development plans – highlighting the point that not even this past week’s Navigable Waters announcement would prevent a property owner from filling the creek if they wanted to*.

And Lisa Jackson, before Army Corps District Director Colonel Mark Toy, County Supervisor Mark Ridley-Thomas, Public Works official Mark Pestrella, and Heal the Bay Executive Director Mark Gold, brought home the point that Compton Creek is an ecological resource – with a history of flooding the community. Post-Katrina assessments of flood levees everywhere has led to a move to increase the flood capacity of the creek, which will be spearheaded by the County and Army Corps. Readers, please don’t take this to mean that a Katrina-like disaster is waiting to surge up from the Port of LA/Long Beach to drown South LA.  However, as readers of Jared Orsi and John McPhee know, the lower LA River environs was a floody place when the LA and San Gabriel Rivers flowed free; the risk is still there. And today’s climate uncertainty is expected to yield high intensity storms (coupled with longer periods of drought) that could overwhelm the system as we know it.

So balancing ecology and flood safety will be a challenge. Here’s a short list of some options to increase flood capacity:

  • Add flood walls to contain more water. The most cost-effective of these options, we could see an increase in ecological benefits if we include riparian habitat in the calculations that set the flood wall heights;
  • Change the channel and right-of-way’s cross-section. More about this below.
  • Buy more land to increase the size of the creek’s floodplain. The most costly option (and viz. above – painful) would be property acquisition and creek widening – but it would also be the option that offers the most in terms of not just ecological bennies but also quality of life for Compton residents. You also don’t have to worry about the possibility of flood wall failures, which was certainly part of the problem in New Orleans;
  • Reduce the riparian vegetation/line it with concrete to increase the flow of water. You really don’t need my comment to this option.

Potential channel configurations, vegetation levels, and flood water surface from the Compton Creek Earthen Bottom Enhancement Feasibility Study

I’ve mentioned before that I was part of a team that looked at this issue on Compton Creek for the Los Angeles & San Gabriel Rivers Watershed Council. The draft report is being finalized, but our preliminary assessment – studied to match the then 2008 existing flood control levels, not the upcoming increased ones – found that modest increases in riparian habitat are possible within the existing flood control right-of-way, by changing the channel’s configuration. Take Protoype B above and add 2-3′ floodwalls and you can actually support pretty nice riparian habitat, including some in-channel trees, for example. If you maintain the channel with one access road instead of two (there are a few places around LA County where you see this), you could widen the creek zone and get even more riparian function. Or consider below, Prototype A turned into a typical section for our report, which changed the channel’s cross section modestly (we were angling for affordable change here). The channel’s existing 3:1 slopes are steepened to 2:1, which widens the floodway; a waist-height floodwall protects one access road and allows the other to be flooded. This change allows the gunnited slopes to be replaced with low, herbaceous vegetation, maintains the wetland vegetation currently in the channel, and provides for trees at the top of the channel. Under this scenario, however, trees that would want to colonize in-channel would be removed.

Typical section of Compton Creek with riparian enhancement and trails. Source: Draft Compton Creek Earthen Bottom Enhancement Feasibility Study.

I hope community members and their representatives in government will use our study as a model to inform the planning as the Corps and County proceed.  And let’s take that lesson from history – increasing the right of way in the short term may be politically painful, but would pay off in the long term.

———–

*I don’t know that any exist.

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