This question has been asked for over years. Although it is a simple question, it does not have an easy answer. The answer is difficult because there are numerous factors and events that helped create and influence the trials.
There was a lot of River Corridor Survey work going on at the time and its benefits for environmentally-sensitive flood defence works were plain to see, because engineers could design their schemes and carry out work using the annotated maps and recommendations produced by surveyors.
But, invaluable though this information was for local conservation staff and river engineers, there was no way of archiving, retrieving, analysing or presenting it in a way suitable for an objective evaluation of the physical state of rivers nationally.
We needed to develop a method that could capture the same type of information, but in a more systematic and repeatable fashion and which could be used to establish a national dataset.
In a radically new approach to river management was being developed by the European Commission. Rather than just chemical and biological assessment of rivers, it required a fully ecological approach and by inference, a way of characterising the physical structure of rivers and assessing how this affected biological communities.
Preparing for this step-change in approach was going to mean something new. The NRA needed to develop a method and supporting database for consistently recording, storing and analysing river habitat data.
A very simple system for evaluating the chemical, biological and physical state of rivers was developed in conjunction with the NRA and material was distributed to all schools in Britain. A simple database was able to analyse data returns from hundreds of schools and the results were published.
At that time the NRA could not provide an objective report on the national state of river habitats. This was an embarrassing shortcoming for the statutory body in charge of managing and reporting on rivers in England and Wales.
Early thoughts Early thoughts on a national approach centred on using aerial photography to extract information for assessing the morphology of rivers. The study concluded that it would be too expensive to commission a national aerial survey and to store and analyse the colour photograph images.
An MSc project on the river Wyre confirmed that aerial photography could not be used alone for characterising river habitat structure and that ground surveys were needed to gain a full picture of habitats, pressures and impacts Sansbury, Twenty years laterthe conclusion may not have been the same because of the incredible advances in technology.
A small team, advised by a project board that included external technical experts was formed to take forward and test a method.
An early show-stopper was the incredible variation of recognition and estimation between experienced river corridor surveyors. A seemingly simple task of estimating percentage cover of river-bed substrates or plants over m or even a m length of river gave surprisingly variable results which meant it was useless for repeat surveys or data analysis.
Surveyors were being required to memorise and recall too much information on site. So percentage estimation was abandoned early on in favour of a more structured and sample-based approach.
The second big stumbling block was determining a unit sample length. Originally, it was assumed, quite reasonably, that a variable sample length based on multiples of channel width would be the best way.BackgroundDietary supplements, such as herbal or complementary nutritional products and micronutrients (vitamins and minerals), are commonly used in .
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