Dear All

I see the problems that we create for ourselves with regard 
to definitions. Here is an Editorial that appeared in the 
ECSA Bulletin number 24 p3-4 1997. It is attached as a Word 
document as well as in the body of the message.

The environmental lawyers have difficulties with estuaries 
as they are not as easy to define as other water bodies. It 
is likely that we will never find one definition to fit all 
types of estuaries, this is why I prefer now to use the 
term restricted environments and then add a subdefinition 
for each type of estuary. For those who want more 
information about our local estuary, the Humber, see 
www.hull.ac.uk/iecs

best wishes

Mike


What is an Estuary? - the Interface Between Environmental Science and the Law.

This question has been raised for as long as we have been studying estuaries - from the major reviews edited by Lauff (1960's) and Ketchum (1980's) to the recent ECSA Symposium held in Gent, Belgium, on Estuarine Gradients (Neth. J Aquatic Ecology 27(2-4) 1993, including the discussion of terms by Donald McLusky). Most recently the question was posed at a recent European workshop (see announcement on page 32) and also it has appeared in legal proceedings in the UK - in both cases we had trouble answering it satisfactorily. 

All students are told that before they can tackle a problem they must define their terms but, despite this, a  degree of uncertainty in our definitions of habitat types has been allowed or tolerated in scientific research. The increasing amount of environmental legislation, however, dictates that we will have to be more specific in defining our terms. For example, until recently, in UK law there have been definitions of freshwaters and tidal waters, the coastal zone and open seas but not an estuary. The repercussions of implementing European Union Directives for Habitats Protection and for Urban Waste-water Discharges has led us to revisit the problem and to rethink the definitions. 

As with many of our areas, estuaries and their habitats have fallen between two stools. For example, Tidal Freshwater Areas (TFA) have been long ignored by estuarine and marine scientists as there is no salt as well as by freshwater workers because the water inconveniently goes up an down on a daily basis. Similarly with fringing vegetated areas - either ignored by estuarine and terrestrial botanists or claimed by both of them. 

An estuary can be defined by geographical, topographical, chemical, biological and hydrographical terms. Ask any group of scientists to put a boundary on an area to denote an estuary and they will differ according to their individual perspectives. This was well illustrated in the UK several years ago when the main nature conservation body carried out a review of estuaries and included some large coastal embayments and not others. Topographical distinctions are relatively easy to make whereas chemical and, to a greater extent, biological ones are not. If estuarine plume areas are included then estuaries extent to coastal areas. In particular, we may conclude that it may be easier to define habitats rather than whole estuaries.

The difficulty is compounded when we require definitions which are suitable for large geographical regions. In using the term estuary, we all know what we mean but is it possible to have a single definition which is expressed in quantitative terms as well as qualitative ones and accepted by environmental managers and lawyers? Unfortunately, it is unlikely that legal statutes will accept a definition that an estuary is that which a competent scientist says it is.

The question of what is an estuary has entered legal discussions during the past two years in the UK following the decision in 1995 by the Secretary of State for the Environment to designate two large estuaries - the Humber and the Severn as coastal. Without going into the large and convoluted discussions, in essence this related to the implementation of the EU Urban Waste-water Treatment Directive and the fact that estuaries and inland waters will be regarded under the Directive as areas sensitive to organic enrichment. The only problem was that estuaries had not been defined rigorously in the Directive.

Under the terms of the Directive and the method of implementation, the level of sewage treatment required in an area will be dependent on the size of the population in the catchment and the hydrodynamic regime of the receiving area. If an area can be designated one of High Natural Dispersion (HNDA) then by definition it can receive sewage and allow it to disperse, degrade and be assimilated without deleterious effects. The ability for this to occur should be demonstrated by carrying out Comprehensive Studies of the water column, nutrients, benthos, sediments, etc. Therefore if an estuary can be designated as a coastal area and thus an HNDA then less treatment is required.

The above case, for the Humber and Severn estuaries, led to the local municipalities taking the Secretary of State to court - they considered that it was not in their interest for the areas to be designated as anything other than an estuary as any alternative designation (as a coastal area) would not produce the higher level of sewage treatment that they desired. The judgement in the court case centred on the definition of an estuary and the functioning of these areas including their ability to receive sewage wastes. The scientific opinion considered that if an area looked like an estuary and functioned like an estuary then there was a good chance that it was an estuary - the problem was how to get this into a legally defensible definition. 

There were several ways of defining the boundary, for example in the case of the Humber estuary:
· the topographical boundary indicated a natural break in the line of the coast, far  downstream of the city of Kingston upon Hull, the area responsible for the sewage and the site of any treatment works;
· the biological boundary would have been upstream of the topographical one but again downstream of Hull as marine organisms penetrate inland;
· the chemical (salinity) boundary would have been offshore into the North Sea due to the plume and the inner estuarine area has a characteristic dissolved oxygen sag;
· the tidal boundary would have been way upstream of the others and the city, and at the tidal limits of the rivers. 

Cartographers had further clouded the debate as the Estuary had long been labelled 'River Humber'. With the exception of the tidal definition, the estuary/coast boundary would not have been as far upstream as that recommended originally by the Secretary of State, who proposed the suspension bridge just upstream of the city. However, with the exception of the topographical boundary, all other definitions indicate areas which oscillate on a short and long-term basis. 

In an attempt to sort out this problem, some quantitative definitions have been proposed, for example - an estuary is an area with <95% of the salinity of an adjacent sea area for >95% of the time. This holds for many temperate areas but not for others and of course will include plume areas thus extending the areas covered by estuarine scientists (empire building?). Many would prefer a biological boundary but of course this is even more difficult to define. For example, Sea-fisheries Protection Officers have considered that a sea area is that which supports species commonly regarded as marine. Given the large estuarine migrations of many marine fish species, especially as juveniles, and the oscillating nature of any designated boundaries, there is an introduced degree of variability unacceptable to legal discussions.
The municipalities for the Humber and Severn won their case and the boundaries reverted to the originally-accepted topographical ones but accepted the salinity reduction at the areas where sewage was to be discharged. It is still not clear whether the increased sewage treatment, because an area is designated estuarine, will be of benefit given the large amounts of organic material naturally entering the (estuarine) system. However, the presumption is that any dissolved oxygen sag will be reduced and, more importantly as far as local public perceptions are concerned, 'aesthetic pollution' will be reduced. Of much wider implication is the fact that the court case required an estuary definition that could be legally defended.

Finally, a request for information from ECSA members - are there any countries worldwide where an estuary is defined in terms which are defensible or have been defended in a court of law? Are there other examples where law and lawyers cannot cope with the uncertainties and variability of estuaries? Any members with views or experiences of this type of interface between our science and legal considerations are invited to contact the Editor.

				Mike Elliott

---------------------- 
Dr. Mike Elliott
Institute of Estuarine & Coastal Studies,
& Dept. of Biological Sciences
University of Hull
Hull, HU6 7RX, UK
Tel. +44 (0)1482 465503
Fax. +44 (0)1482 465458 (Dept.)
     +44 (0)1482 465001 (IECS)
[log in to unmask]
www.hull.ac.uk/iecs