Dear New Zealanders,
Today was really exciting at Lucas Creek. We built probably the first rock vane in New Zealand, maybe the southern hemisphere! Those of you who have accessed the NCHRP Report 544 or the ESenSS manuals (www.esenss.com) know that “REDIRECTIVE” techniques (Rock Vanes, Bendway Weirs, etc) are often cost-effective and environmentally-sensitive alternatives to ” RESISTIVE” techniques such as rip rap, gabions, automobiles, refrigerators etc.
The research commissioned by Transportation Research Board (NCHRP 544 / ESenss) compiled documentation that Vanes, for instance, produce a scour pool at the tip and slow water adjacent to the bank. This substrate complexity provides much more habitat, as several fish counts and bio-assays demonstrated.
What is really cool about vanes is they redirect the high flow velocities away from the bank. Two rock vanes can move the thalweg away from the bank 20% of the stream width. Therefore, with no impinging flows against an outer bend, the bank can be protected with more vegetative type measures. One vane will convert actively eroding banks into depositional areas both upstream and downstream of the vane!!!
Also, we got much of this weeks work area all “buttoned up” with Compost Blankets (2-3″ (50mm) thick) and some compost berm. Compost is not new here in NZ but this project gaining lots of attention so seeing the use of Compost Blankets (these are the “Eco-Blanket type), Compost Socks (“Living Walls”), Compost Silt Socks, and, my favorite alternative to silt fence, the Compost Berm should help with more widespread acceptance.
I’m reminding everybody here about the Caltrans sponsored research done in California and the new SSPs recently developed for Compost Blankets, Compost Socks, and Compost Incorporate ( see https://www.dot.ca.gov/hq/LandArch/ec/index.htm)
Well here is the “living wall” built on a rock toe. The purpose for this structure is to protect a tree we need to save while maintaining a long, rather deep pool. As mentioned before, one of the ways Lucas Creek has historically dissipated its’ energy is undulations in it’s long stream profile (pools and glides). This pool in the bend is pretty important to maintain.
The treatment for steep banks is a rock toe and maybe some incorporated large woody material (remember, the other historic energy dissipator is woody debris). When impinging flows hit hard, immovable objects the flows generally go down and scour. That is just what we want for aquatic habitat, a nice sustainably maintained scour pool with overhanging wood maybe.
Come winter time, the living wall – the compost socks and geogrid facing, will be hydromulched. IECA Member, Robert Coulson, RST Environmental Solutions Ltd., has has much experience building and vegetating these compost sock/reinforced walls, especially successful repairing failed road embankments. Robert often incorporates willow brushlayering in his solutions. Unfortunately, willow species are not native to New Zealand therefore willow must be kept out of the Lucas Creek Biotechnical Restoration.
We will also build several Newbury Rock Riffles along this 800m stretch. Rock riffles are a environmentally-sensitive grade control structure and we are using them to ensure that future incision of Lucas Creek will be arrested. They are also strategically placed to maintain the pool and glide profile. Newbury Riffles are well described in the NCHRP Report 544 – Environmentally-Sensitive Channel and Bank Protection Measures (2005) or also available in ESenSS. www.esenss.com.
Stay tuned, next entry will show compost blanket being installed and the first-ever rock vane to be built in New Zealand (maybe in the entire Southern hemisphere! )
Got a lot done on Thursday and Friday! This job requires major earth moving (DIRT Moving) and we got major resources allocated. There was a bit of reluctance to put lots of “diggers” (excavators) and dumps trucks on until there was a good understanding and confidence in strategy.
The North Shore Council and Auckland Regional Council (planners, regulators, etc) have been “in the loop” and have approved the methodology to do the work yet protect the resources. For instance, the idea of damming the creek and diverting water around the work area, then pumping out immediate work area, then trapping eels and craw fish, etc, WAS FRAUGHT with Problems.
While it sounds reasonable, the overall effect was much more turbidity than wanted, for a longer period of time, and a badly degraded bottom (from walking on the soft substrate). Also the dams leak causing turbidity. Took us a day to seal the dam as best we could. Secondly, laying the diversion pipes in an “incised stream” was also turbidity producing. Thirdly, when you pump water around site it ended up causing erosion or extremely turbid water downstream – an option would be to require a huge sediment pond (here they use flocculant and decanters (lot like Skimmers – see our episode on Sediment Ponds)). And finally, walking thru the stream to rescue eels and crawfish causes EXTREME damage to bottom and even more turbidity.
So, our new protocol and methodology is to “stay out of active stream, period”. When we build structures in banks or bottom, we will use “clean” rock and wood. We will minimize touching the active bottom with equipment. Using clean, “self-launching rock” was, in fact, almost the entire reason for success of our projects in Alberta. (See Hinton I and II, and Willow Creek). We are monitoring the water quality and if a problem occurs we will stop, find out what happened, and re-evaluate.
The agency representatives are very pleased with the way things are working. Please notice that we have left a vegetated berm (called a bund here) between the disturbed banks and the stream. Also not that the “back slope” of the bund is steep so any clods or soil fall away from the water. We are also limiting the actual work in the stream, e.g., when we remove the bund, to 50 meters.
Do you mean that it is even conceivable to to work near a stream without building a silt fence?? I say this so mockingly because silt fence near streams are most often an utter failure – more on that stuff later.
On Monday we are all ready to build some more structures – Living Walls with Compost Socks, Rock Toes (looking natural), Large Woody debris – Keep Coming Back !
What is this Lucas Creek Project all about you might ask!
Well Lucas Creek drains a large watershed that happens to be one of the fasted growing areas in the Auckland area. New shopping malls, the huge new Rugby Stadium, and a good part of the Motorway are just some of the developments. On the good note, North Shore City Council and Auckland Regional Council (ARC is also the ultimate regulatory authority here) are implementing considerable Low Impact Development (LID) development standards. They are way “ahead” of us in California. But the point is, Lucas Creek is and will continue to experience higher and more frequent flood type flows.
So the main purpose for this project is to “re-fit” the creek to accept new flow regimes and to maintain water quality, enhance aquatic habitat, and develop a sustainable regional park area. All the goals center around Lucas Creek operating in a Proper Functioning Condition (PFC). PFC criteria asks can the stream system pass water (low and high), sediment, bedload etc., in a way that is naturally sustainable. A good question to ask is how did the stream dissipate excess energy in the past, e.g., rocks, meanders, large woody debris, pools/riffles, access to flood plains, or car bodies and refrigerators !!
Back to what we are doing. We are working over 800m long stretch this phase and we are going to widen Lucas Creek. It has already incised about 2-3m and the high flows rarely go out of bank. It is not functioning properly now and can only get worse with continued urbanization. The bottom width, low flow, will be roughly doubled to 4-5m. There are a couple of wide radius inner bends that will have large, low terraces (point bars) built. Next is the installation of really cool, naturalized grade control structures – Newbury Rock Riffles, will arrest any future incision. They will also provide good substrate, encourage pools and riffles and …… that will be shown and discussed next week!!
Good news, while it rained last night and a bit today, the creek has stayed pretty clean. The most turbidity we saw today came during the mid day rain but the murky water came above our site, probably the Motorway upstream!! One of the other neat things is we are demonstrating NEW and Effective BMPs, alternatives to silt fence, like fiber rolls (installed with Caltrans-approved Type 2 installation – rope and stake method), and compost silt socks (half chips/half aged compost). These worked GREAT last night, and unlike silt fence, could be moved around today!
The pictures taken today show the completion of a “living wall” with rock toe. This is our “model” treatment for how we might treat other steep outer bends (versus the low, wide and terraced inner bends). We also introduced some salvaged Large Woody Debris as that is how this clay/silt soft-bottomed stream historically dissipated energy.
Also, upstream, two large excavators and an off road dump are “hogging out” soil (got dirt!) for a flood terrace there. Our operators are so good, keeping a 1 meter berm between them and the live stream – not a clod has fallen in!!
John again from New Zealand. Here are a few more thing of erosional interest, call it “erosion control around the world”
During the big Hobson Highway Deviation Project field tour I learned they were trying an innovative “green wall” for a highway bridge. The six-inch thick reinforced concrete wall had holes it it. Behind the holes were Delta-lok geobags. The bags were filled with growth medium. Native plants “plugs” were then inserted into the bags. Another experiment they had going was to try it with an additional geotextile between the bags and the concrete. What do you think??
I got to hook up with Robert Coulson again. Robert had taken all of my classes at the IECA Conferences (and I think anything else IECA had to offer) and to see him again was so gratifying. Robert has brought all that knowledge and technical expertise to New Zealand. He has several hydroseeders, mulch/compost blowers, straw blowers AND he is growing and propagating a shrub willow that is very useful for Bioengineering projects – which he has done many!
Note Salix sp. are not native to NZ and most see them a s a nuisance. However, digging a little deeper I discovered that the “BAD” willow here are a tree willow growing along streambanks. These willow trees are referred to as “Crack Willow”, not a drug thing but they “crack and break off and then cause flooding”. Soooo Robert is using an shrub willow for brushlayering, and quite successfully. He is building ‘live walls’ for road repair using compost socks (Filtrexx) and brushlayering. These projects and all his others have been so successful and cost-effective that Robert’s company is getting quite a good reputation in this island nation. Maybe we can post some of these projects in the future?
Also, check out some of the cool stuff the North Shore City Council has going on.
I am GOING to Fiji, no kidding
More from there, Ciao John
Hi all, John here!
Well I made it to Auckland New Zealand. I’m here for IECA Australasia Chapter’s Erosion and Sediment Control Conference. I’ll be giving a keynote and teaching some courses.
It was a Very long flight. I left Redding late afternoon on Wednesday and arrived in NZ at 4 pm Friday. I don’t know where Thursday, June 18th went!!!???
On my way to the hotel, I spied the highway from the airport was under construction. And I saw some really well constructed storm drain inlet protection. While silt fence inlet protection is not my first choice, these were exceptionally well placed and installed. Good job mates!
It is winter here after all. So, there seems to be active erosion and sediment control going on and I am really looking forward to the IECA Australasia / NZ Institute of Highway Technology Conference. While I’ll be teaching and lecturing, I always learn a lot whenever I leave the good old USA.
After the conference next week I’ll be caravanning around the country for a couple of weeks. I’ll keep you posted on all things erosion and stream restoration.
If you’re at the conference, find me and say hi!
Note: That fantastic illustration up at the top is courtesy of the very talented, very wry Sam Posnick. Check her out at www.SamPosnick.com
Hey All, James Here:
Whoops! I was just informed from a reader that Kangaroos do not actually inhabit New Zealand. They are indigenous to Australia only.
Sorry all for the mix up. My fault. I let the unbridled joy of seeing a smoking Kangaroo wearing a party hat override the need for fact checking…I’m easy that way.
So for the purpose of this blog entry, lets all assume that the Kangaroo above is just visiting New Zealand (likely in for the conference).