Micro

What this scale means

Micro scale covers interventions at the level of a single site, a field, a parcel or a short reach of a watercourse: a leaky dam in a ditch, a retention pond, a restored strip of riparian vegetation, a change in the way one field is cultivated. The decision-maker is usually a landowner, a farmer, a catchment group or a single municipal department, and the budget is small enough that a formal appraisal is often skipped altogether.

The assessment problem at this scale is not complexity but evidence. The intervention is cheap, so the cost of assessing it properly can exceed the cost of the intervention, and no one is going to commission a distributed hydrological model to decide about a pond. What is needed instead is a method that establishes what the measure achieves from measurements that can be taken locally, and a way of expressing that achievement in terms that a larger decision — a water company's investment programme, a flood authority's plan — can use.

What to use

Low-cost connected monitoring is the instrument that makes this scale assessable. A pair of stations, one upstream and one downstream of the structure or one inside and one outside the treated area, measures the difference the intervention makes, and a soil moisture station does the same for a change in land management. The measurement is converted into a volume of additional storage and expressed as a proportion of the flow at the asset of interest, which is the form in which the result becomes useful to anyone else.

Where the measure is proposed rather than built, the classification scheme for Nature Based Solution selection processes provides a route from the local problem to a shortlist of measures that are known to suit it, including the criteria that eliminate unsuitable options and the disservices that each measure can bring.

For a group wanting to demonstrate achievement rather than to appraise an option, the FreeStation training material takes a participant from building a station to reading the natural flood management analysis functions, and it is written to be followed without a commercial relationship to the equipment.

Where it is used at NAIAD

Micro-scale measurement and demonstration were applied in the Glinščica catchment and in the Lower Danube demonstration area, where the effectiveness of individual measures had to be established without a full modelling programme. The monitoring work at these sites is the reference for what a small-scale assessment can support and what it cannot.