Targets first of all need to be realistic and appropriate to the desired objectives. For example, the recent move for a change in target for the Combined Sewer Overflows (CSO) spills from a frequency figure (e.g. number of times per year) to a required water quality needs understanding and put into context with any proposed measures that could influence them. Any predictions used to satisfy targets need to be appropriately interpreted [MOD01]. A comprehensive monitoring regime is needed [CAS05]. Monitored data should then be fed back into the predictions in order to improve them, i.e. generate realistic measures against the targets to effectively guide proposed installations. The current Tunnel scheme will still result in a number of spills per year and achieve a "moderate" water quality. How does this compare with an optimised grey and blue-green alternative solution?
There are many elements to generating effective plans. The London Plan 2011 [GAI07] is a comprehensive document covering many areas of our life in the city. Once a new framework to support and promote BG strategies is in place, a view should be taken to see whether this Plan needs revision to maximise the impact of Blue-Greening in London and to act as a template for our other cities. Incentive schemes, such as those in use in Philadelphia [CAS05], may be required to maximise the impact of any plans.
One of the key elements to good planning and targetting is modelling. A system to determine how individual boroughs' BG plans and actions measure up to the London Plan may need to be formulated. Blue-Greening generates many benefits within many areas (see Home Page) and so clarity is needed on the benefits derived from different measures. Plans are also needed for when conditions are exceeded as all grey and blue-green solutions have a specified limiting performance.