Land and Water•November/December 2006

by Pete Romocki and Chris Matthews

Note: This original project was writtenup in Land and Water Magazine inDecember of 2004.

Project Background:THE Little Sugar Creek

Environmental Restoration Initiativeencompassed a stream restoration, green-way trail development and overallenhancement of a stream corridorthrough the greater Charlotte, NorthCarolina metropolitan area. It covered a15-mile section of Little Sugar Creek run-ning south from Uptown Charlotte to theNorth Carolina/South Carolina state line.Phase 2 of this initiative was a joint effortbetween Mecklenburg County and theEEP known as the Freedom Park StreamRestoration Project. The EEP-fundedproject was one of the largest of its kindin the state, placing more than 1,500 lin-ear feet of stream on a new alignment asmuch as 150 feet from its current loca-tion. The Little Sugar Creek flowsthrough the entire length of FreedomPark, a distance of more than 4,500 linearfeet. Freedom Park is in a highly urban-ized setting two miles south of the centralbusiness district. The 14-square-milewatershed is virtually built-out, with theonly development occurring on in-filllocations. Therefore, urban runoff andstorm water are the main contributors tostream degradation along this section ofthe creek.

Historical records indicated thatLittle Sugar Creek was likely channeledand straightened in the early 1900s toimprove storm water conveyance andallow urban development to occur on thefloodplain. In the 1970s and ’80s, thecreek was showing signs of instabilitydue to upstream development, so a con-crete and grouted rip-rap liner wasinstalled along the banks to provide sta-bility and prevent erosion. The streamremained in this state for the next 25 to30 years.

In 2002, Mecklenburg Countyawarded a contract to demolish the con-crete banks in preparation for the upcom-ing restoration project. The demolitionran concurrently with the design and permitting of the channel restoration.

In 2003 a restoration of Little SugarCreek that passes through Freedom Parkwas commissioned. HDR, the nationalengineering consulting firm, and a localenvironmental specialty f irm, HabitatAssessment and Restoration ProgramInc., were selected to design the projectbased on past experience in the water-shed, availability to devote technicalexpertise and other resources to this com-plex project and a familiarity that hadbeen formed through previous work withEEP. The team performed an extensivewatershed survey, a sediment transportstudy, a reference reach analysis and asite survey to achieve a permittable andstable design. The final design incorpo-rated natural channel techniques toenhance and create habitat, provide stabil-ity, improve water quality, control stormwater runoff and provide a more aestheti-

cally pleasing stream ecosystem.

Project Update:Approximately one year after the

completion of the initial project someareas were experiencing significant ero-sion on the stream banks. Specifically,this was occurring at locations whereplanted vegetation had failed due to nutri-ent poor soil conditions and where thestraw/coconut erosion matting that wasused to initially preserve the diverse cus-tom seed mix was no longer in place.

The problems developed along areas ofthe stream banks that were experiencinghigh shear stress loads from occasionalintermittent high volumes of storm water

S T R E A M R E S T O R A T I O N

www.landandwater.com

Freedom Park StreamRestoration Project Repair

Restored stream project. Photo taken September 2006 by Doug Smith.

Approximately one yearafter the completion ofthe initial project someareas were experiencingsignificant erosion on thestream banks.

Land and Water November/December 2006•

flow. The owner of the project sitebought attention to these stream bankareas of concern and the engineer, HDRtook on the task of correcting the defi-ciencies in the stream banks design. Theoriginal work included installation of rootwad sections in high velocity areas. Therepair effort of this project only involvedsome of the original straw/coconut ero-sion blanketed areas.

The initial design of the streambanks utilized a jute netted coconut/strawerosion blanket to protect the banks fromthe expected high shear stress loads. This

product was selected because of its abilityto completely biodegrade. Coconut/strawerosion blankets typically have the abilityto withstand shear stresses in the 2.0 to3.0 pounds/square foot range after beingvegetated. Evident after the fact was thatflow conditions were exhibiting shearstresses considerably greater than whatbanks without vegetation could survive.Typical stream bed erosion protection isaccomplished using turf reinforcementmats (TRMs). TRMs are composed ofnonbiodegradable materials, usually sometype of plastic, and can survive shearstresses of 10 lbs./ft2 or more after beingfully vegetated.

HDR chose not to use TRMs becauseof the non-biodegradable nature of theproduct. It can be detrimental to the envi-ronment as snakes and other fauna thatinhabit riparian areas have been seen get-ting caught in the plastic matrix, particu-larly the nettings. HDR has also made ita point to design their stream projectssuch that the combination of slope andvegetation allow for a stable stream bank.

If the soils allow proper vegetativegrowth and the banks have been con-structed properly, based on a thoroughexamination of the hydraulic pressures inthe system, TRMs may not be necessary.The issue at Freedom was that theextremely poor soil conditions preventedthe establishment of temporary and per-manent vegetation. This was especiallytrue of the woody vegetation which

provides a root mass adequate to keepstream bank soils in place during floodevents. The banks were thus vulnerableto the high velocity floods that occur inthe park with the original erosion materi-als selected.

The Freedom Park project had strictenvironmental requirements from HDR tobe constructed with materials that werecompletely biodegradable. This require-ment eliminated the option to use tradi-tional TRMs. In the redesign of the failederoded areas HDR surveyed the market-place for other available options.Selected was a combination of biodegrad-able erosion blanket materials. Utilizedwas a netless excelsior blanket (CurlexNetFree) and a heavy woven 700 gm./ sq.meter coir mat used in combination witheach other. The coir mat was installed ontop of the netless excelsior and both wereanchored down using wood one foot long

wooden stakes approximately every 2square feet (Ecostakes).

The repair work was completed by afour man crew in about four days byNorth State Environmental, Inc. Theyhydroseeded the cleared banks using abrowntop millet variety grass seed. Thenetless excelsior blanket was theninstalled onto the seeded banks and final-ly the heavy woven coir matting was laid

down on top of it and staked. The con-tractor installed the netless excelsior blan-ket on a large area and had the intentionof installing the coir mat over it the nextday. Unfortunately a significant stormoccurred that evening and damaged theentire area that had been laid. They wereable to reclaim most of the netless excel-sior fiber, redistribute it and then secure itwith coir mat. The lesson learned is toinstall the coir mat on top of the netlessexcelsior as soon as possible to preventdamage.

Significant rain had also occurredless than 10 days after the installation andthe repaired areas appeared to have heldup good during this first test. The sitewas again inspected six months lateragain with very good results. Vegetationhad become well established and thecombination of blanket materialsappeared to be doing the trick.

S T R E A M R E S T O R A T I O N

www.escn.tv

Exposed coir mat where vegetation is still being established. Photo taken 2006 by DougSmith.

Evident after the factwas that flow conditionswere exhibiting shearstresses considerablygreater than what bankswithout vegetation couldsurvive. Typical streambed erosion protection isaccomplished using turfreinforcement mats(TRMs).

Land and Water•November/December 2006

In September 2006 the project wasonce again inspected and found to be sur-viving well. This was an experimentalproject for HDR in that it is the first case

where a net free product was installedunder coir mat as a “composite” solutionfor a stream bank restoration project.Stream bank restoration projects are

unique in that all biodegradable “natural”components are required. It makes ero-sion control of high shear stress levelareas difficult because TRMs cannot beused. The use of Curlex NetFree as a partof a component system for protectingstream banks in high shear stress areas isnow part of HDR’s arsenal of solutions.L&W

For more information, contact Peter Romocki, American Excelsior Company, (770)645-5853 or e-mail: promocki@curlex.com.

S T R E A M R E S T O R A T I O N

www.landandwater.com

Installation of coir woven mat on top of net free excelsior using one foot long wood stakes.Photo taken May 2005 by Pete Romocki.

Unfortunately a signifi-cant storm occurred thatevening and damagedthe entire area that hadbeen laid.. The lessonlearned is to install thecoir mat on top of thenetless excelsior as soonas possible to preventdamage.