Resources

Checklists

These checklists will help you achieve best practice in erosion and sediment control:

Glossary

Abatement Notice: A legal warning that can only be issued by council enforcement officers. It warns the recipient that he/she is contravening the provisions of the Resource Management Act 1991 (RMA).
AEP: Stands for “annual exceedance probability”. A statistical term that defines how likely an event is to happen annually, which is used as a basis for calculation and planning. Eg, a 5% AEP event like a severe rainstorm has a 5% chance of being exceeded in any one year.
as-built: A plan which is drawn up after the design and/or build has been created.
attenuate: To weaken, eg in the case of water flow.
baffle: A semi-permeable or solid barrier put into a sediment retention pond to deflect or regulate flow and even out the speed, to create better conditions for sediment to settle.
batch dosing: Applying a measured amount of flocculant to dirty water in a single dose. Also called shock dosing.
batter: A slope built to a uniform gradient. A gentle backwards slope.
biaxially-orientated: A material with two axes or directions, eg plastic netting.
bonded synthetic fibre mats: A three-dimensional geomatrix nylon (or other synthetic) matting with more than 90% open area, to facilitate root growth.
bore: A hole or tunnel made by using a drill-like motion with a tool called a bore.
bund: An embankment shape that is made to hold back water. Can be made of various materials, including earth, compost and hotmix.
butt: To butt something, eg joints, means to push them up against each other tightly.
conduit: Any channel, open or closed, that conveys water.
contaminated: Land is contaminated when the soil contains any hazardous substance that could be a threat to human health or the environment.
contour: A line across a slope connecting points of the same elevation.
contour drain: Contour drains or cut-offs are temporary excavated channels or ridges, or a combination of both, constructed across the contour of an area of land that has been disturbed by earthworks.
crimping: Using implements to embed straw mulch into soil.
CTMP: Stands for Chemical Treatment Management Plan, also called a Flocculation Management Plan (FMP).
cut-off: Contour drains or cut-offs are temporary excavated channels or ridges, or a combination of both, constructed across the contour of an area of land that has been disturbed by earthworks.
dam: A barrier that confines or raises water for storage or diversion, to create a hydraulic head, to prevent gully erosion, or to retain soil, rock or other debris.
dead storage: The component of impoundment volume that does not decant and remains in the DEB. It is important for dissipating the energy of sediment-laden inflows. Also called permanent storage.
decant rate: The rate at which surface water is decanted from a sediment retention pond.
decanting earth bund (DEB): An impoundment area formed from a temporary bund or ridge of compacted earth.
deposition: The accumulation of material when its transporting agent, eg water or wind, slows down.
design storm: The storm of annual return probability, used as a basis for calculations and planning – for example, a 5% annual exceedance probability (AEP) storm.
dewatering: Removing impounded water from excavations, tunnelling, trenches, stream diversions and sediment control devices. This could be groundwater or surface water. Usually done by pumping.
“dirty” water: Water that contains sediment, often because it has run through a works area.
dispersion: The process where a material’s chemical and physical properties allow it to be easily dissolved, broken down and washed away.
dispersive soil: Its chemical and physical properties allow it to be easily suspended in water and washed away.
disturbed area: An area of exposed soil.
diversion: A non-erodible channel or bund that conveys clean water runoff or concentrated flow.
drop out pit: A pit within the dirty water diversion that allows heavier sediment particles to drop out before they enter the sediment retention device.
entrained: The movement of soil by raindrop impact, overland flow or wind.
ephemeral: A stream or watercourse that only flows for part of the year.
erosion: The physical, chemical or biological processes that wear the land surface away by detaching and moving particles of soil.
ESC: Stands for “erosion and sediment control”.
estuary: An area where freshwater meets salt water, and where the tide meets the river current.
fill: Earth that is placed, and usually compacted, to raise the land surface.
fines: The silt- and clay-size particles in soil.
floc sock: A segmented, geosynthetic sock filled with reagent in dry flake form. Dirty water runoff flows over it, dissolving and mixing with the reagent.
flocculation: Flocculation makes suspended sediment particles in liquids come together to form larger, heavier particles or ‘flocs’, that settle faster. This is often achieved by a chemical treatment. Flocculation happens after coagulation. For effective sedimentation, you need to use both tools.
flume: A pipe drop structure or flume is a temporary pipe structure or constructed flume placed from the top to the bottom of a slope.
FMP: Stands for Flocculation Management Plan, also called a Chemical Treatment Management Plan (CTMP).
forebay: A sediment forebay is an impoundment, basin, or other storage structure designed to dissipate the energy of incoming runoff, and detain the runoff for initial settling of coarse particulates. Forebays are different from sediment basins because they are usually used to pre-treat runoff before it discharges to the primary water quantity and quality control tool.
friable: Easily crumbled. Used to describe soil.
geotextiles: Permeable fabrics, which means that liquids or gases can pass through them. Geotextile products include mats, plastic covers and erosion control blankets, and range from those that physically shed water to those that incorporate seed and mulch and support vegetation while protecting bare soil. When used on soil, they can stabilise and protect. They are also very useful for dust control.
gypsum: A naturally occurring, soft crystalline material which is a hydrated form of calcium sulphate. It is mined from deposits, and is organic and non-toxic. It comes in different textures and densities, depending on usage. Used as a coagulant.
ha: Stands for “hectare”.
HAIL: Hazardous Activities and Industries List
hydrology: The science of how water behaves, in the atmosphere, on the surface of the earth and underground.
hydroseeding: Pressure-spraying a slurry of water, seed, fertiliser and paper or wood pulp over a surface, to revegetate it.
impermeable: Water or other liquids or gases cannot pass through it. Often used of materials, eg rocks and soil.
impervious: Water or other liquids cannot pass through it. Often used of surfaces, eg roads, or materials, eg plastic.
impound: To enclose and hold back, eg dirty water.
intermontane: Between mountains or mountain ranges. Can include basins that are being infilled by sediment eroded from surrounding mountains.
jute: A natural fibre that is made into a yarn and loosely woven into a mesh.
live storage: The volume between the decant outlet level and the crest of the DEB primary spillway. Also called decant storage.
LLUR: Stands for “Listed Land Use Register”. Canterbury’s LLUR.
loess: A highly erodible soil. There are deposits of it throughout New Zealand, including in Banks Peninsula and the Port Hills.
MHWS: Stands for “mean [which means, average] high-water spring tide”.
mixing zone: A designated area of a stream, river, lake or artificial watercourse into which wastewater or pollutants are permitted to empty. The wastewater mixes, usually by natural means, with cleaner water. Water quality standards are permitted to ‘exceed’, or in other words, ‘be worse’ in a mixing zone, but only if this will not degrade natural habitat, public health or recreation.
mobilised: Moved away from its previous location, eg by wind or rain.
MSDS: Stands for “Material Safety Data Sheet”.
mulch: A covering put on the surface of soil to protect it, eg from raindrop impact, and to improve germination. Straw (wheat or barley) and hay are the most commonly used materials, but mulch can also be bark, wood residue and wood pulp.
overburden: In mining, overburden is the material that lies above the targeted rock or mineral resource.
overtop: When water overflows or runs over the top of the material that is intended to contain it.
PAC: Stands for “poly aluminium chloride”. A common flocculant reagent.
perennial: Lives for a few years.
Permitted Activities: Activities described in the Resource Management Act, regulations or a plan or proposed plan that do not require a resource consent if they comply with standards, terms or conditions, if any, specified in the plan or proposed plan.
photodegradable: Can be chemically broken down by exposure to light.
pipe drop structure: A pipe drop structure or flume is a temporary pipe structure or constructed flume placed from the top to the bottom of a slope.
plastic mesh: An open-weave geotextile made of an extruded synthetic fibre woven into a mesh with an opening size of less than 50 mm.
plastic netting: A lightweight netting for securing loose mulches like straw to soil surfaces, to establish vegetation.
PPE: Personal protective equipment, eg safety and/or high vis clothing, footwear and equipment.
receiving environment: The final endpoint of the discharge.
rehabilitate: Restore to as near to pre-disturbance conditions as possible.
riparian: Riverbank.
rip-rap: Loose rock. A layer of large stones used to protect soil/shorelines from erosion.
riser: In a sediment retention pond, the riser is a vertically-placed pipe to which decant pipes are attached, which forms the inlet to the primary spillway.
RMA: Resource Management Act 1991
roughening: roughening the surface of unstabilised earth surface (bare soil) – either with horizontal grooves across the slope, or by tracking with construction equipment.
runoff: Surface water runoff (also known as overland flow) is the flow of water that occurs when excess stormwater, meltwater, or other sources flows over the earth’s surface.
scarify: To break up the soil surface.
scour: The erosion effects of flowing water.
sediment: Solid material, both mineral and organic, that is in suspension, is being transported, or has been moved from its place of origin by air, water, gravity or ice and has come to rest on the earth’s surface either above or below water.
sediment retention pond (SRP): A temporary pond made by excavating natural ground, or building an embankment, or some combination of the two.
seeding: Planting and establishing grass.
settle out: When sediment sinks to the bottom and stays there as sediment, while the treated, cleaner water is discharged.
sheet flow: Shallow, dispersed overland flow.
silt fence: A temporary barrier of woven geotextile fabric that captures mainly coarse sediments carried in sheet flow.
silt sock: A mesh tube filled with a filter material. This material should be compacted, and could be compost, sawdust, bark or straw, depending on what the sock is to be used for. Also called filter sock.
slake test: Submerging dry soil in clean water to assess how dispersive the soil is (how easily it can be suspended in water and washed away).
slurry: A fine, semi-liquid mixture, used in hydroseeding.
SMP: site management plan
sodic soils: Have a higher percentage of sodium (salt) than other soils. Chemical forces in sodic soils stop the suspended sediment from settling.
soil binders: Soil-stabilising agents (also known as polymers). They form a cohesive membrane or protective crust that reduces windblown dust generation. They might be liquid or powdered, and organic (eg guars, latex or various other timber resins) or chemical (eg acrylic copolymer, anionic bitumen emulsions or cementitious gypsum- or lime-based). They are sometimes called soil-stabilising agents.
SSMP: Stands for “site-specific safety management plan”.
stabilise: To protect exposed soil from erosion.
staging, staged construction: Doing earthworks in smaller sections and over time, while progressively revegetating the site.
stormwater inlet: A barrier across or around a catchpit or a water sensitive design device (eg, a raingarden).
straw blankets: Machine-produced mats of straw with a lightweight biodegradable netting top layer. The straw should be attached to the netting with biodegradable thread or glue strips.
strike: Grass strike is successful fertilisation and growth. The minimum density of strike to stabilise soil is 80% coverage.
super silt fence: A temporary barrier of woven geotextile fabric over a chain link fence that captures mainly coarse sediments carried in sheet flow.
surface roughening: Roughening the surface of unstabilised earth surface (bare soil) – either with horizontal grooves across the slope, or by tracking with construction equipment.
surface runoff: Rain that runs off rather than soaking into or being held on the surface.
swale: A depression or dip in the land surface without flowing water, that can be seasonally wet.
synthetic fibre with netting: A mat of durable synthetic fibres treated to resist chemicals and UV light. It is a dense, three-dimensional mesh of synthetic fibres stitched between two polypropylene nets.
tamp: To push or pack down.
T-bar: A floating dewatering device that allows for the decanting of the cleaner surface water from the top of the water column.
tensile strength: How resistant a material is to being stretched or torn.
terrigenous: Derived from land.
toe (of slope): The bottom of a slope, where it stops or levels out.
topography: The physical features and layout of an area, including natural and built features.
topsoil: Soil with suitable organic and structural properties to go on top of land to provide a fertile medium for vegetation. It gives some protection to the subsoil layer and increases the soil’s absorption capacity, because it holds more water than clay subsoil layers.
total suspended solids (TSS): Solids in water that can be trapped by a filter. Can include silt, decaying organic matter, industrial wastes and sewage. The dry-weight of the particles is a water quality parameter used to assess the quality of wastewater.
treatment train: Applying a series of erosion and sediment control tools and techniques progressively throughout your project, as required by the circumstances.
turfing: Establishing and permanently stabilising disturbed areas by laying a continuous cover of grass turf.
turkey’s nest: A ring of silt socks, with a pumping discharge point in the centre of the ring.
utilities: Includes electricity, gas, water, wastewater and telecommunications.
velocity: Speed.
viscous: Thick and sticky.
watertable: The ground is saturated with water below the watertable level.
wood fibre blankets: Made of biodegradable fibre mulch with extruded biodegradable netting held together with adhesives. Designed to enhance revegetation.

References

Auckland Regional Council. 2003. Stormwater treatment devices: design guideline manual. ARC Technical Publication No. 10. (ARC TP10).
Cathcart, S. (HEB Construction Limited), 2016, A recipe for Excellence in Sediment Control – A Low Technology Approach at the Huntly Section of the Waikato Expressway, International Erosion Control Association Conference, Auckland, New Zealand, September 2016.
Erosion and Sediment Control Guideline (2007), Environment Canterbury, R12/14.
Erosion Control Treatment Trials on Port Hills Loess: Cashmere Catchment 2016, EOS Ecology Report No: ENV01-15035, August 2016.
Hunter, G.G., Lynn, I.H. & Phillips, C.J. June 1996. The susceptibility of land in Canterbury to soil erosion and water quality degradation associated with earthworks and vegetation clearance. Unpublished Environment Canterbury report no. U96/23, prepared by Manaaki Whenua Landcare Research.
Leersnyder, H., Bunting, K., Parsonson, M., and Stewart, C. (2016). Erosion and sediment control guide for land disturbing activities in the Auckland region. Auckland Council Guideline Document GD2016/005. Prepared by Beca Ltd and SouthernSkies Environmental for Auckland Council.
Lynn, I. July 1993. Land types of the Canterbury region. Unpublished report prepared by Manaaki Whenua Landcare Research for Environment Canterbury.
NIWA. March 1993. Sedimentation and erosion in the Avon-Heathcote catchment and estuary.
Trangmar, B. 2003. Soil conservation guidelines for the Port Hills. A report prepared for Christchurch City Council. Landcare Research Contract Report: LC 0203/111, May 2003.

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