Stormwater Monitoring.


Stormwater litter monitoring methodology summary v1.0

Additional downloads and supporting documents can be found on our Beach page — head there to download them.

Data entry

'Official' stormwater litter monitoring training is currently in development. For now, you can enter 'Ad Hoc' stormwater litter data. Just click on the button below and select 'Conduct an Ad Hoc survey' on the next screen.


Methodology summary: Stormwater litter monitoring

This methodology is a localised adaptation of the United Nations Environment Program / Intergovernmental Oceanographic Commission Guidelines on Survey and Monitoring of Marine Litter and Mountains to Sea Wellington’s Drains to Harbour programme. Note: This is a methodology overview intended for Citizen Scientists. It does not replace official training, which covers important Health and Safety, logistics and planning considerations.

Choose Survey Area

  • This methodology is for monitoring catchpits using a gross pollutant trap such as a LittaTrapTM. 
  • Sites should be chosen with safety in mind first. Optimal locations include parking lots or a cul-de-sac. Sites must be adjacent to a foot path and not on a bend in the road which could obscure visibility of passing cars.

Set up Survey Area

  • The catchpit trap must be installed prior to monitoring with permission from your local council or property manager/landowner. Record the installation date. 
  • Complete a site risk assessment before each ‘Litter Survey’. 
  • You may also have a Traffic Management Plan to follow which will be provided by the council. Set up road cones around the catchpit to alert traffic. 
  • At the catchpit take 2 photos: 
    (1) Facing the catchpit from above 
    (2) Of the roadway.
  • Also record your visual assessment grade (A-D) for the site immediately surrounding the catchpit.

Complete Litter Survey

  • Brief ‘Citizen Scientists’ on Health & Safety. Provide clean-up/survey equipment (gloves and high-vis vests). 
  • Sweep any debris around the edges of the trap into the trap. 
  • Remove the trap, carry it away from the road and empty it into a bin on the footpath or grass berm. The drain must be closed after removing the trap. Return the trap to the catchpit.

Complete Litter Audit

  • While you can do this on site, it can be easier in a sheltered location like a garage or a school. Some items can be dangerous, so follow health and safety instructions. 
  • Sort all litter from the survey area into the categories provided. Use the sieve to separate any items under 5mm, so that they aren’t counted or weighed. 
  • Group items from each category in one of your sorting bins. Record the item count and total weight (in grams) of the items in each category. Also record confidence level (High or Low) for weight. 
  • Record your visual assessment grade (A-D) for plastic resin pellets. 

Repeat Regularly

  • To get long-term data and insights on our litter problem, surveys should be repeated regularly, at least every 3 months but preferably monthly. 
  • Catchpit monitoring differs from beach and stream litter surveys in that the trap may overflow with litter or leaves at particular sites*. You may need to repeat your litter survey more often at certain sites or during certain times (more frequently in the autumn due to leaves or during the winter due to rain)**.
  • This is a great chance to get back together with your friends, whānau and/or colleagues to look after the places you love. 

* If your trap is overflowing to the point that litter could not properly enter the trap, make a note in the comment section that the sample is compromised.
** If you are unable to keep an eye on your trap for an extended period of time (e.g., over summer) you can remove the trap from the catchpit and replace it when you return. Enter the date of reinstallation of the trap in the 'Date Last Emptied' field.


Data quality

Quality Assurance and Quality Controls are currently in development.


Health & Safety

Stormwater-specific health and safety documents are coming soon.