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.

Looking downstream at the outer bend in Lucas Creek just before it flows under a bridge (on right). Gavin is shown here preparing the keyway for a redirective Rock Vane. Rock Vanes point upstream at a 30-degree angle and dip from a high water elevation down to the stream bed.

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.

Rock Vanes are best built of self-launching stone (poorly sorted, well graded) but I like to place some big anchor stones also.

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!!!

Next we placed the self-adjusting, self-launching stone. The average highwater here is expected to be as high as the excavator bucket! Even so, I predict that the vegetated bank behind the bucket will remain stable and that deposition will occur on the bank-side of the vane. Any bets?Next the Compost Blanket was used to stabilize the bare soil and provide erosion control. The Caltrans EC Studies at San Diego State University showed that Compost Blanket provides 96% reduction in erosion!!

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.

When compost blankets are placed over properly scarified soils, as we did here, one can expect greatly increased infiltration rates and soil water holding capacity. Also, the compost can absorb 10-times its weight in water, acting as a sponge to slowly wet even clayey soils! Also, also, compost provides soil microbes that are essential for sustainable plant establishment. Also, also, also, the compost organisms slowly convert the carbon into nutrients that the plants can use. FYI, properly made and aged compost does not remove available nitrogen, e.g, the carbon:nitrogen ratio is very low. Check out the Compost Berm !! This can have SO MANY applications as a silt fence substitute. How many of you have had to put in a silt fence down by the stream edge?? Is it not impossible to properly key in – often resulting in unnecessary soil/rock disturbance? Well, just put in a compost berm instead, it will catch rocks and clods and certainly capture silt or sediment from sheet-type flows. Grasses and vegetation will become established in the berm and – YOU NEVER HAVE TO RETRIEVE IT. No excess disturbance after project is stable, no silt fence going to landfill/dump. NO, properly aged compost doesn’t discharge N to waterways (EPA). No, properly aged compost doesn’t float or wash! What is not to like?Representatives from the North Shore City Council, the owners of Lucas Creek and the Park Reserve, are frequent visitors to the project. There is a lot of interest, curiosity and support for this project. Downstream view of Pool, Newbury Rock Riffle (actually a “viffle”), NZ Modified Lunker (LWD), Compost berm, Rock Vane, and Compost Blanket.

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.

This picture is looking downstream. The impinging point for high flows will be about where the rock is being placed.

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.

The same bend with rock toe & wood incorporated. From this secure base we will construct a “live wall” built from compost berms & geogrid for a reinforced soil wall.

The geogrid (biaxial) is laid back a meter then wraps the face of three compost berm “lifts” (about 18″ or 0.5m)

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.

As my friend David Derrick says, “Be the water”! Imagine the high water, another meter high hitting the wood, and rock toe. It (the water) will try to undercut the bank but instead maintain the long pool, we hope!

Here is an upstream view of the completed living wall transitioning into an “engineered, log” undercut bank, sometimes called a lunker structure. This log structure might more accurately be called a “modified New Zealand log lunker”! Notice also just downstream is a newly completed Newbury Rock Riffle. The crest of the riffle is actually a modified cross vane, so I call it a “viffle”!

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.

The Modified New Zealand Log Lunker almost completed. Looking upstream 

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! )

G’day M8s!

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!!