STORM is a sustainable design assessment tool that can be used to assess whether best practice water quality objectives have been achieved for a development site. 

The rating is a percentage out of 100% and the higher the rating, the better the score.

A development has achieved best practice measures when it achieves a 100% storm rating. This translates to a 45% reduction in the usual annual nitrogen levels.

The rating takes into account factors including:

• Impervious surfaces and their sizes
• Site area and location
• Water treatment type and size
• Number of occupants in a building

This tool, used in conjunction with others, assesses how sustainable a development plan is and results are usually used in SDAs (Sustainable Development Assessment) and SMPs (Sustainable Management Plan).

It facilitates the planning process and highlights opportunities for sustainable design improvements, including energy, water and waste efficiency, liveability and running costs.