The coastal zone is being seen increasingly as a major resource requiring the planning of its use to accommodate the many and frequently conflicting demands placed upon it. In the U.K. this planning is complicated by the difficulties arising from the scale, map projection and quality of information provided by the different mapping agencies. These difficulties are compounded because the representation of information concerning the littoral is quickly outdated by the dynamic coastal processes operating in this zone. This paper presents the results of an investigation of the use of digital remote sensing and mapping techniques, using data from a set of LANDSAT MSS scenes corresponding to different tidal states, for mapping within the coastal zone where regular and possibly cyclic map revision is required.

The principles of airborne thermography are outlined. A general introduction to instrumentation, imaging and data correction methods is included, along with particular examples of some of the methods used. Specific applications of work done on Tay Estuary and English Channel imagery are described to illustrate some of the results which can be achieved.

A new mathematical model has been constructed for tidal motion and level in the Tay Estuary. The model is based upon the two-dimensional vertically integrated equations of motion and gives two-dimensional vector velocities and levels from the rail bridge to the Bar, about 5 km east of Buddon Ness. The extent of the model outside the mouth of the Tay is 3 km north of Buddon Ness and 7 km south. The equations of motion are expressed in the form of central differences in space and solved explicitly in time using the Local Integral Method. The emergence and submergence of drying zones in the estuary are calculated during the tidal cycle. A representation of the hydrodynamic resistance of the road bridge was included in the model.

The boundary conditions for the model were based upon estimates of river flows at the western entrance and tidal levels at the eastern, northern and southern boundaries. Boundary conditions at the eastern end of the model presented considerable complexities because of the presence of an amphidromic system to the south of the Norwegian coast. The final solution adopted was to choose tidal levels along the easterly boundaries to give velocities in the outer estuary that agreed with available tidal atlases of the region.

Velocities and levels at intervals of 250 m for the period of a tide show the prevalent shoaling conditions over the estuary combined during certain periods with conditions of high velocity, giving very difficult approaches to the River Tay.

In a mathematical model of the Tay (Gunn & Yenigun 1987) based upon the Local Integral Method (Gunn & Yenigun 1985), tidal levels at the seaward boundaries and velocities at landward boundaries are used in setting boundary conditions, so that validation studies are mainly based upon changes in internal tidal levels, and comparison between computed and measured velocities within the modelled region. The comparisons of tidal levels within this estuary over a 5.0 m tide showed agreement with overall values from Buddon Ness to the rail bridge, but within the overall agreement there were significant differences in the immediate vicinity of the road bridge. Velocities predicted within the estuary have been compared with measurements provided by a number of surveys in the period from 1972-78. The agreement between experiment and prediction was good in the central and western regions of the model, but the comparison between measurement and prediction was less good near the eastern boundaries. The principal reason for poorer agreement in the east was the difficulty in setting boundary conditions at the open sea extremes of the model. The most satisfactory way of improving the model near the open sea boundaries would be to link the model for the Tay with a model for velocity and level in the North Sea.

A numerical model based on a Galerkin finite element solution of the one-dimensional salt transport equation is used to simulate the unsteady longitudinal distribution of salinity in the Tay Estuary. Tidal discharges are provided by the hydrodynamical equations of motion and continuity whose solution is coupled to that for the transport of salt. Dispersion coefficients used in the model are estimated with the aid of field data collected during a spring and neap tide. These coefficients are shown to vary with longitudinal position.

A method of predicting coastal changes north and south of the Tay Estuary, due to the action of waves and wave-generated nearshore currents using computer simulation techniques, is described. The computation is based upon a wave refraction procedure, using as input data the deep-water wave climate (height, period and direction of approach) and the bathymetric characteristics of the sea area from Montrose to Fife Ness. The technique provides a prediction of the longshore component of wave energy flux at breaking, by computing the wave energy dissipation through shoaling, refraction and friction of the waves, for a number of points along the 70 km of shoreline. Potential patterns of longshore sediment transport are then derived in order to establish zones of potential erosion, transport and deposition between Boddin Point and Fife Ness.

The occurrence of a population of the spionid polychaete Marenzelleria viridis (Verrill 1873) in the middle reaches of the Tay Estuary is reported. This is a new British and European record of a North American species, and its principal characteristics are described and compared with earlier accounts. Size frequency analysis of the population showed it to be dominated by large animals from July 1984 to May 1986. The population matured coelomic gametes during winter 1985–86 and spawned in March 1986 to produce a heavy settlement in May, which subsequently grew rapidly. The distribution of M. viridis in relation to other species, sediment and other ecological parameters is described from a single survey of the Invergowrie Bay mudflats. Marenzelleria population densities of up to 1500 m 2 were negatively correlated with all other species of a low diversity macrofaunal community dominated by predatory polychaetes and filter feeding bivalves. Marenzelleria was abundant down to sediment depths of 20–30 cm. The significance and origin of this population is discussed.

The spatial distribution of different physiological groups of bacteria (nitrifying bacteria, nitrate respiring bacteria, clostridia, phototrophic bacteria, sulphate reducing bacteria and methanogens) has been determined in the surface sediments of Kingoodie Bay in the Tay Estuary. The overall distribution of the different microbial populations is largely dependent upon the presence or absence of O2, i.e. populations of obligate aerobes were greater at the surface where O2 was present, but with increasing depth and hence anoxia were successively displaced by populations of facultative and then strictly anaerobic bacteria. Thus, maximum rates of nitrification, an oxygen dependent process, were recorded in the 0–10 mm depth horizon (098 μg of N per g dry weight of sediment per day) while nitrate respiration rates were maximal in the 10–20 mm horizon (2.92 μg N per g dry weight of sediment per day). Dissimilatory sulphate reduction at 20–30 mm depth (102.1 n mol SO42 reduced g dry weight sediment -1.d -1). Methanogenesis was similarly recorded at all depths investigated but higher rates were recorded at 40–50 mm depth (22.64 n mol CH4 produced g dry weight sediment -1.d -1). These data are discussed in relation to the physico-chemical factors which arc generated in these estuarine sediments and which not only govern the spatial organisation of individual microbial populations but also modulate their metabolic activities.

The sediments of the floor of the Tay Estuary are dominated by assemblages of quartzo-feldspathic sands, although pebbles and silts are locally important. The sands are principally of inorganic materials, but they include shell fragments which account for up to 25% of the material, depending upon locality.

Detailed analyses of the shell components of the 0.3–1.2 mm size fraction (400 particles from each site) in the area between Balmerino and Monifieth Bay reveal the presence of much molluscan debris (identified as mature and immature bivalves and gastropods), with significant proportions of bryozoan, barnacle or echinoderm skeletal fragments according to locality. Ostracoda and foraminifera are less common. The shelly material occurs mostly within zones inhabited by the same living organisms.

The characteristic blue-coloured Mytilus edulis shell fragments are also recognised up to 6 km landwards of the westernmost known colonies, along the railway bridge.

Shell matter is dissimilar in shape and surface texture to the clastic grains and large shell fragments are frequently associated with sand sized inorganic sediments, which have been shown in flume experiments to respond in a similar manner to hydraulic controls.

The Mytilus is therefore suitable for use as a natural tracer. It indicates up-estuary net residual motion of sediments in the middle and upper reaches. This pattern confirms evidence from heavy mineral assemblages that North Sea derived sands enter the estuary and migrate westwards to accumulate on the upper estuarine tidal flats.

In the upper Tay Estuary the marshes bordering the northern intertidal mud-flats are dominated by Phragmites communis in the west, with Juncus gerardi becoming more important eastwards, where Aster tripolium is also significant. Sedimentation on the surface of the marshes at Kingoodie and Invergowrie has been measured at monthly intervals over a twenty-three month period, using stake implants to provide local marker levels. The marsh surfaces were at their greatest heights in early summer and fell during autumn and winter. Maximum accretion rates were measured in spring on the outer marshes at both sites, where net accretion over the entire period was greatest. The net accretion in the Phragmites marsh was 2.5 mm, in the Aster belt 5 mm, in established Juncus 9 mm and in newly colonising Juncus 8.7 mm, whereas on the adjacent Kingoodie mud flats there was net stability over the twenty-three-month interval. Accretion was less at Invergowrie (3–5 mm) than at Kingoodie (2.5–9 mm). Monthly analysis of the upper 0.5 cm of the surface sediments showed the Invergowrie marsh sediments to be sandier than those of Kingoodie. Silts and clays deposited on the outer marsh surface in spring migrate landward during the summer and autumn. The apparent annual net accretion varied greatly with the specific month used for comparison, with 13 mm net losses based on November figures and 10 mm gains using January data.

The suspended loads at three stations in the middle estuary of the River Tay have been analysed monthly, at low and high water of the spring tides, over the period June 1983 to May 1984. Major mineral modal analyses were derived from bulk and mineral oxide analyses. The concentrations in the suspended loads of the trace metals Cr, Cu, Pb and Zn were determined. An efficient circulatory system operates within the middle estuary which largely retains the suspended loads acquired from the inner estuary, even at seasonal periods of high influx. The major mineral assemblage is quartz, chlorite, illite and kaolinite. There is some preferential landward return of quartz and chlorite. Chromium has an association with chlorite, while copper, lead and zinc seem linked with suspended particulate organic matter which, at least in part, is derived from sewage disposal into the estuary. Dissolved zinc is associated with dissolved organic matter.

The River Tay and its estuary is one of Britain's largest and most important aquatic systems. Rising at 625 m and flowing for 148 km the River Tay is the largest by flow in Great Britain and has a catchment area of 5031 km2. There are considerable ecological changes from source to estuary. These take the form of transitions, but four main aquatic communities can be recognised: an upper, base-poor, swift-flowing alpine section, then an oligotrophic section with moderate flows at lower altitude, next a much richer, slower flowing, more lowland stretch and finally the upper estuary itself. The problems of classifying and conserving running water systems are discussed and the importance of the Tay system is emphasised. The linear form and catchment size of larger rivers makes it difficult to give them—particularly their lower reaches and estuaries—full conservation protection. The River Tay is sufficiently unique, both physically and biologically, to warrant further scientific investigation and nature conservation protection.