Intertidal Deposits

River Mouths, Tidal Flats, and Coastal Lagoons

Eisma Doeke, Doeke Eisma

• Publisher: CRC Press
• Year: 2019
• Print ISBN:
  9780367400668
  9780849380495
• eBook ISBN:
  9780429605642
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Biology

Intertidal Deposits: River Mouths, Tidal Flats, and Coastal Lagoons combines the authors personal and professional experience with the mass of available literature to present a cohesive overview of intertidal deposits and the widely diverse conditions of their formation worldwide. This includes the strong influence of water movements, climate, sediment particle characteristics, vegetation, fauna, and man.   Intertidal areas are important for many reasons both scientifically and economically and recently, a growing concern for conservation of these fragile regions strives to preserve and protect their natural balance. This book, written by an international expert in the field, concentrates on the more important intertidal areas distinguished by size and morphology, tidal range, the degree and type of vegetational cover, the amount and type of benthic fauna, the extent of human exploitation, and the degree of previous study.

1

Worldwide Distribution of Intertidal Areas

On the basis of the data given in The World’s Coastline (Bird and Schwartz 1985) and the literature referred to elsewhere in this book, the most important intertidal areas can be listed as follows:

Europe: The Wadden Sea, the Wash, the Bay du Mont-St. Michel, and the Bassin d’Arcachon. Along the remaining coasts of Britain, France, and Portugal small areas with intertidal deposits occur in estuaries, rias, and bays. In the White Sea the tidal flats are probably extensive but not much studied. In the fjords of Norway and the Faroer, tidal deposits are virtually absent.

Africa: The lagoons from Guinea-Bissau to Benin (with the Volta river delta), the Niger delta, the lagoons and bays in Cameroon and Equatorial Guinea, the Zaire river mouth, the lagoons and deltas in Natal and Mozambique, and the open-coast mangrove flats in Tanzania. From Morocco to Senegal along the Sahara coast, intertidal deposits are rare and small with larger deposits at the Banc d’Arguin, but become more numerous and extensive in lagoons and river estuaries from the Senegal river mouth to Sierra Leone. Also between Equatorial Guinea and the Zaire river mouth, intertidal deposits are present in bays, lagoons, and behind spits. South of the Zaire river mouth only small intertidal areas are present in Langebaan lagoon and near Port Elisabeth. In Tanzania and Kenya and along eastern Madagascar, rather large intertidal areas are present in bays, lagoons, estuaries, and deltas. Along Kenya and Somalia, they decrease in size (and number).

South Asia: The sebkhas along the southern Persian Gulf, the Indus delta with the Rarrn of Kutch and the Bay of Khambhat, the deltas along the Indian east coast, the Ganges delta area, the Irrawaddy delta, the Chao Phraya river delta, the Mahakam delta in Indonesia, and the open coast flats along the Mekong river mouth and the Red river delta. Smaller areas with intertidal deposits are present along the Persian Gulf and the northern shore of the Indian Ocean up to the Indus river delta. From Burma to the east the intertidal deposits are relatively large because of the large sediment supply from even small rivers. In Indonesia relatively large intertidal areas covered with mangrove are present along eastern Sumatra, south and east Kalimantan, south Irian Jaya, and the adjacent coasts of Papua, New Guinea, but their sediments have been little studied.

North and East Asia: South and West Korea, Bohai Bay (Yellow river delta), the China mainland coast between Shandong and Fujian (Jiangsu coast, Chang Jiang estuary, Hangzhou Bay, Wenzhou Bay), West Taiwan, and the Zhujiang river mouth. Small intertidal areas are present along the Shandong peninsula and along the Chinese coast from Wenzhou Bay to west of the Zhujiang river mouth. Large intertidal areas are present along the northern Gulf of Anadyr, West Kamchatka, the northern Sea of Okhotsk with the Bay of Penzhinskaya, and along Sakhalin and smaller areas along northern Siberia, but little has been published about them. No intertidal deposits are present north of 73°N.

Australia/New Zealand/Large Pacific Islands: The west and northwest coast of Australia, (Shark Bay to King Sound), Cambridge Gulf-Van Diemen Gulf-Arn- hem Land, river mouths in the Gulf of Carpentaria, and Broad Sound. Numerous smaller intertidal areas occur along the other parts of Australia, New Zealand, and the larger Pacific islands as part of river deltas and in bays.

America West Coast: The Mackenzie River delta, the Yukon and Kuskokwim deltas, Bristol Bay, Cook Inlet, the Queen Charlotte Islands, San Francisco Bay, the Colorado river delta, the Colombia coast, and the Gulf of Guayaquil. There are no intertidal deposits north of 70°N. Numerous small deposits are present in bays, river mouths, and lagoons from Alaska to Ecuador. Hardly any tidal deposits are present from northern Peru to central Chile. Small intertidal deposits occur in the fjords of southern Chile.

America East Coast: San Antonio Bay, the Amazort-Guyana-Orinoco delta coast, the Mexico-Texas lagoons, the Louisiana-Mississippi delta coast, the SW coast of Florida, the Sabellaria reefs in western Florida, the bays and marshes in Georgia and North and South Carolina, the Bay of Fundy, and the St. Lawrence estuary-Labrador-Hudson Bay flats. Smaller intertidal flats are present along most of the American west coast from Tierra del Fuego to Greenland and, in particular, between Boston and Nova Scotia. As along the American west coast, no intertidal deposits are present north of 70°N.

The tidal range, tidal type, and wave height characteristics for these areas are given in Table 1.1, based on data given by Davies (1972). The wave characteristics are given for the open coast that is exposed to waves coming from the coastal sea or ocean. Where waves are relatively high (Bassin d’Arcachon, Bay of Fundy), it should be realized that the intertidal deposits here have been formed in well-protected bays.

Many river mouths on tidal coasts contain small areas of intertidal deposits along estuaries and deltas. They are mentioned where they have been the object of sediment studies. For a number of large coastal areas sedimentological information on intertidal deposits is limited and only a general description can be given. This concerns northern Russia from the White Sea to the Gulf of Anadyr and the Sea of Okhotsk, Alaska, Iceland, the Philippines, north Australia, Tanzania and Kenya, and parts of the South American east coast. For the sake of completeness, these are included in Chapters 2,3, and 4, Statistics on the occurrence and extent of tidal flats, salt marshes, and mangrove are available for western Europe, the east coast of the U.S., and Australia. They are given after Table 1.2 in Table 1.3, Table 1.4, Table 1.5 and 1.6.

TABLE 1.1
Characteristics of the Most Important Intertidal Areas Tidal Range

TABLE 1.2
Frequency of Waves >2.4 High and Largest Waves at the Most Important Intertidal Areas

TABLE 1.3
Area of Tidal Flats in Europe

TABLE 1.4
Area of Salt Marsh on the Atlantic (Tidal Coasts of Europe)

TABLE 1.5
Distribution of Salt Marshes and Mangrove (Florida) Along the U.S. East Coast (Gulf of Mexico Coasts Not Included)

TABLE 1.6
Areas of Bare Mud Flats and Mangrove Mud Flats along the Australian Coast

1.1. Tides

The tidal range of coastal waters ranges from less than 5 cm along the eastern part of north Siberia and in the so-called tideless enclosed seas (Mediterranean, Black Sea, Caspian Sea, the Baltic, and the Red Sea), to more than 15 meters in the Bay of Fundy in eastern Canada. Davies (1964, 1972) and Bird (1970), followed by Hayes (1975) and many others, have distinguished a microtidal regime with a tidal range between 0 and 2 meters, a mesotidal regime with ranges between 2 and 4 meters, and a macrotidal regime with tidal ranges larger than 4 meters. Barrier islands and river deltas develop particularly in microtidal areas, inlets, and tidal deltas at tidal ranges of up to about 3 meters, and tidal flats and salt marshes predominantly in meso- and macrotidal areas. Ehlers (1988) proposed a modified classification based on observations made along the North Sea: a microtidal regime at a tidal range less than 1.4 meters, and a mesotidal regime between 1.4 and 2.9 meters, but this still leaves a large tidal inlet with a large ebb tidal delta (the Texel inlet in the western Wadden Sea with a tidal range of 1.2 meters) in a microtidal area. Sha (1989) therefore pointed out that for tidal inlets the tidal prism is a better measure. The distribution of tidal range (in meters at spring tide) along the world’s coasts is given in Figure 1.1 (from Davies 1972). The actual distribution of tidal range may vary more at short distances than is indicated because of regional and local changes in topography and water depth which may induce a larger or smaller tidal range than can be indicated on the scale of Figure 1.1. Figure 1.1 and Table 1.1 indicate that there is no relationship between the presence of intertidal deposits and the tidal range: 25 of the intertidal areas listed in Table 1.1 are along a microtidal coast, 15 along a mesotidal coast, and 28 along a macrotidal coast. Ten areas are along coasts with both micro- and mesotidal ranges, three along coasts with meso- to macrotidal ranges, and five along coasts where the tidal range varies from micro- to meso- and to macrotidal. Also the distribution of all intertidal deposits, as indicated in Chapters 2, 3, and 4, does not seem to indicate that the presence of intertidal deposits is related to the tidal range.

FIGURE 1.1 Distribution oftidal range along the world’s coasts, in meters at spring tide. (From Davies 1972. With permission.)

FIGURE 1.2 Distribution of tidal types along the world’s coasts. (From Davies 1972. With permission.)

Nor does the tidal regime seem to be an important factor for the presence or absence of intertidal deposits: 52 of the areas listed in Tables 1.1 and 1.2 occur along coasts with a semidiurnal tide, 24 along coasts with a mixed semidiumal/diumal tide, and two along coasts with a diurnal tide. When the areas are added that have one tidal regime in one part and another regime in another part, the numbers become 58, 32, and 4, respectively. This distribution reflects the worldwide distribution of tidal regimes (Figure 1.2). The semidiurnal tide has two high tides and two low tides within approximately 24 hours, and there can be a relatively small daily and fortnightly inequality in tidal range. Diurnal tides have only one high and one low tide within about 24 hours, while mixed tides show a sequence of a low low tide, a low high tide, a high low tide, and a high high tide. As pointed out by Davies (1972), the tidal regime determines the duration of drying out between tides. Differences in the length of this period may affect the degree of sediment consolidation during the dry period and, in warm climates, the salt concentration in the sediments. The tidal regime also affects the distribution of organisms in the intertidal zone and the intensity of tidal currents, which is related to the time that is available to move water masses. Ginsburg et al. (1977) introduced an “exposure index” as a distinctive parameter, which is related to the surface elevation above an arbitrary level (me...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• Marine Science Series
• Author
• Preface
• Introduction
• 1 Worldwide Distribution of Intertidal Areas
• 2 Macrotidal Deposits
• 3 Mesotidal Deposits
• 4 Microtidal Deposits
• 5 Wind Flat Deposits
• 6 Morphology of Intertidal Areas
• 7 Intertidal Sediments: Composition and Structure
• 8 Sediment Transport in Intertidal Areas
• 9 Intertidal Fauna and Vegetation
• 10 Holocene Development of Intertidal Deposits
• 11 Influence of Man
• References
• Author Index
• Subject Index
• Index of Geographical Names
• Latin Fauna Names
• Latin Flora Names