Estuary History
The following text is taken from a Report entitled 'The Humber Estuary - A selection of papers on present knowledge of the estuary and its future potential given at two symposia arranged by the Humber Advisory Group and the University of Hull' dated 20 January 1979.
Synopsis
NV Jones, Department of Zoology, University of Hull
History
The Humber has been formed by the amalgamation of several rivers running from West to East, breaking through the chalk wolds and later being forced into a south-easterly direction by an ice front. The development of the existing drainage system and more recent changes in the course of the main channels resulting from natural changes and man-made developments are discussed by de Boer in Chapter 1.
The movement of channels within the Humber Estuary is a continuing process. In the upper Humber, channel migration tends to be faster than further downstream and important changes which have taken place since the beginning of the century are discussed by Denman in Chapter 2.
In the lower Humber, the present main channel is similar to that shown on the earliest English chart with soundings, dated about 1560; changes in sea level have, however, caused significant changes in the configuration of the coastline in this region. For example, the area from Sunk Island to Spurn had settlements in pre-Norman conquest times but these were abandoned when the sea level began to rise late in the 13th century leaving a shoal - Sunk Island. A reduction in the rate of rise of sea level in the 17th century stimulated reclamation activities during which Sunk Island and Cherry Cob Sands were recovered. Shoals in the upper estuary have also been the basis of the reclamation of both broomfleet Island and Read's Island in the 19th century.
Spurn Peninsula is an unusual feature of the outer estuary and historical studies show that the present spit is the fifth for which records exist. Previous spits seem to have followed a cycle of growth and destruction lasting about 250 years; artificial stabilization has however prevented, but only just, thedestruction of the present spit for 100 years longer than might otherwise have been expected.
Physical features
The main approach channel to the Humber leads through New Sand Hole and divides into three channels south of Spurn Head: Hawke Road, Bull Channel and Haile Channel where depths vary between 9 and 16 metres at Low Water. West of Grimsby the channels merge to give deep water (12-19 m at Low Water springs) exploited by the Immingham Oil Terminal. The channel then crosses to the north bank at Hull where Low Water depths are 9 m or more. As indicated above, these outer estuary channels have been relatively stable for a long time but those to the west of Hull are much less reliable with the main navigable channel changing from the south side of Read's Island to the north bank and back again with a cycle time of up to 20 years.
The British Transport Docks Board (1) accumulated a great deal of physical data which was used in designing and operating a large model of the estuary for research purposes. Unfortunately this model is no longer functional (2). Some of the data quoted by Denman in Chapter 2 are summarised here to give a general idea of the dynamics of the estuary.
The tidal cycle in the outer estuary is nearly sinusoidal with a 6.25 hour ebb and flood component. At brough however, the ebb tide extends over 8 hours and the flood for 4.5 hours. The volume of water passing Spurn Head during a spring tide is about 1.7 x 109 m2 but only 60 per cent of this during a neap tide. The freshwater input averages about 246 cumecs with an increase to about 1550 cumecs at times of flood, The Humber is generally a well-mixed estuary with salinity varying by less than 5 per cent with depth. On a winter spring tide there can be as much as 3 x 106 tons of silt carried in suspension but only about a third of this would be suspended during a summer neap tide. This suspended load varies with position in the estuary and stage of the tidal cycle, it is also affected by temperature arid freshwater discharge.
now Associated British Ports (ABP)
This is a reference to the physical model of the Humber Estuary that once stood on the site of what is now Port House, ABP’s local headquarters. A wholly-owned subsidiary of ABP, ABPmer, continues to operate a mathematical model of the estuary at its base in Southampton.
The substrata of the intertidal areas are predominantly muddy but the central bed is mainly fine to medium sand with some local gravel and boulder clay exposures. The movements of the sediments both within the estuary and in the adjacent parts of the North Sea require further investigation
Chemistry and pollution
The Rivers Ouse and Trent contribute an average daily flow of 246 cumecs to the Humber of which about 14 cumecs are sewage effluent and 12 cumecs are trade effluent. A further 2.5 cumecs sewage and 3.1 cumecs trade effluent are discharged directly into the Humber.
The regional water authorities (Anglian, Yorkshire and Severn-Trent) and their predecessors have been monitoring several chemical and biological parameters and such surveys are planned to continue. In Chapter 3 Urquhart summarises the work that has been carried out and also draws attention to the production by the Water Research Centre of a one-dimensional time dependent model for the estuary which, it is hoped, will provide a basis for the future management of the tidal waters.
Dissolved oxygen rarely falls below 50 per cent saturation in the middle and outer estuary but in the area to the west of brough it is very variable, the range recorded being from zero to supersaturation. This oxygen sag in the upper estuary is a long-standing one and possibly partly natural; it has however been improving in recent years, a situation which can be correlated with improvements in the condition of the River Trent.
Extreme values of oxidised nitrogen range from 0.4 mg 1-1 at Spurn to 12.0 mg 1-1 at Trent Falls. Ammoniacal nitrogen in the Ouse and Trent has shown a decrease since 1964 which is related to an associated increase in oxidised nitrogen. Levels of ammonia at Killingholme have however remained more or less constant at 0. 1 mg 1-1.
Heavy metal analyses of estuarine water have posed some practical difficulties but records are kept of metal levels in both sediments and organisms, particularly with respect to certain discharges. Determinations of copper, zinc, lead, cadmium and iron carried out by L. H. Jones and discussed in Chapter 4 showed considerable variability between species, seasons and different years. Generally, organisms in the Humber carry metal loads similar to animals from estuaries classed as reasonably unpolluted with respect to these elements. Metal levels in sediments and organisms were generally higher from within the estuary than from the coastal regions outside, but no study was made of the relationship between the levels recorded and the nature of the sediments.
Biology
Both benthic and intertidal surveys (see Urquhart, Chapter 3, and Jones and Ratcliffe, Chapter 5) have shown the expected increase in diversity of animal life from the freshwater to the seaward end of the estuary, the benthic surveys have produced over 100 taxa of macrofauna with diversity ranging from 0 to 24 taxa m-2 and numbers ranging between 0 and 88,600 individuals m-2 towards the seawards end. Intertidal regions have yielded at least 75 taxa including larger algae, with the higher levels of the shore generally being more productive than lower zones. This is probably associated with the stability of the sediments. Macoma balthica is a particularly common bivalve in the outer estuary (Spurn Bight) and has been the subject of detailed production studies; it has been found to have an average P:B ratio of 1:0.75 and a mean annual production of 12.0 gm m-2.
The biology of young fish in the Humber Estuary is discussed by Riley in Chapter 6. Plankton samples taken in the outer Humber are generally of high biomass but poor in fish eggs and larvae compared with samples from coastal sites. Pelagic eggs were found of only the sprat, sole, flounder and dragonet and at total densities of no more than 1 egg rn-3, about one quarter of the figure for the open coast. Catches of fish larvae in the outer estuary are also low in terms both of variety of species and total larval density. These results are, however, not significantly different from those of some other estuaries that have been studied.
Surveys of young and small fish on the nursery grounds in the estuary showed 24 species, most of the catch being of flatfish (plaice, sole, dab, flounder and turbot) and gobies. Another 17 species made up less than 25 per cent of the catches. An indication of the distribution patterns of some species has been obtained. For the two principal commercial species for example, young plaice were found from west of Hull (salinity 7‰) to the coast; sole were not however found above Immingham, although experimentally this species can withstand almost freshwater. Its distribution in the Humber may be controlled by the type of sea bed available and the strong tidal scour.
The Humber ranks amongst the top six British estuaries with respect to wintering populations of waders. The figures for redshank, knot and dunlin recorded in 1971/72 by the BTO/RSPB/WFT Birds of Estuaries Enquiry (Cutts, Chapter 7) represented about 10 per cent of the British and Irish totals for these species. The mallard roost in the upper Humber produced the highest figures of the national survey.
There are two areas of prime importance to birds; the National Wildfowl Refuge in the upper Humber which is a roost for ducks and geese and the flats of the outer estuary which are the feeding areas for most species, but particularly for the waders. The Humber can be justifiably regarded as of national and international importance with respect to birds, and developments on this and other estuaries may affect this status.
Uses of the estuary
Commercial exploitation of fish stocks is an activity long associated with the Humber but landings of fish solely from the estuary are difficult to determine (see Theaker, Chapter 8). Some boats from Grimsby use long lines for cod during the winter, with considerable year-to-year variation in success. Pot fishing for whelks is carried out on the south bank and for crabs and lobsters mainly on the north shore. The cockle beds to the east of Grimsby have been declining since 1971, probably due to the weather and the instability of the beds, and no longer support any full-time gatherers.
There is quite a lot of part-time fishing from various bases including trawling for shrimps and soles, lining for cod, shore angling for cod, whiting and flatfish, as well as push-netting for shrimps and fyke-netting for eels. It is clear that fishing as a full-time activity is decreasing, mainly due to economic pressures and the unreliable catches. However, fishing as a leisure activity either from small boats or from the shore seems to be increasing.
Studies of the use of Humberside for leisure activities have shown that the estuary has had little attraction in the past. This seems however to undervalue its potential (see Patmore, Chapter 9). The water surface, of the estuary as well as associated freshwater bodies, can certainly stand an increase in use but this is likely to remain limited to a minority group. The estuary banks have a scenic attraction of their own and can be used for informal recreation. However, access is rather limited and very few sites are developed in any sense for recreation, although there are considerable possibilities such as at Paull, the waste tips at Hessle, the Humber Bridge and the Town Docks. These possibilities are compared with the achievements of Liverpool and Detroit in providing country parks in similar areas and New York where the bridge has been used as a focus of the Gateway National Recreation Area.
There is no overall scheme envisaged for recreation in the area but the estuary could be used as a focus for such activities and in this sense the river could become the vibrant heart rather than the lifeless core of the area.
Future developments of the estuary feature prominently in Humberside County Council's Structure Plan. Two of its six key Issues are directly related to the estuary: Development in the vicinity of the Humber Bridge and industry on the Humber Estuary (see Hunter, Chapter 10).
Humberside has a present population of 848,000 and in general, the Structure Plan envisages a growth of about 4.5 per cent in the next 15 years. However, the area, and particularly the estuary, has features that may attract considerable conflict of interests particularly from the economic and environmental viewpoints. The County Council has the unenviable task of attempting to reconcile those interests and has adopted interim policies as a starting point. These allow for developments but in a controlled way which will be related to the site and nature of the proposal. Developers on the estuary must show that the use of such a site is necessary for their operations. Housing developments will be mainly based on present centres and on some selected villages and transport links are being greatly improved, with west-east motorways and the Humber Bridge already under construction. It is hoped that the concept of open government now employed by the planners will help to resolve some of the future problems by allowing people to be more involved in the process of planning.
Conclusions
We have, then, a general picture of a large estuary with an interesting past and the possibility of a more important, and in some senses, an exciting future. It lies in an area which still has considerable development potential and is still a relatively unpolluted estuary. There have been limited studies of the water body in the past but activity has increased in recent years although most of this is still of a descriptive nature. We still know very little of the processes that occur in the estuary or of its importance on a national and international level.
Such information may well be required in the near future as an input into the process controlling developments in and around the estuary, developments that are clearly given a high priority by regional government.
The history section of the HES web is being developed and ABP HES is grateful to Dr Neville Jones for his permission to use this extract. Keep a look out for further information and links.