4
Gerardo M.E. Perillo· M. Cintia Piccolo . Mario Pino-Quivira
mally these estuaries are associated to large discharge rivers that either by their
coastal setting (e.g., de la Plata River) or the relatively strong coastal dynamical
processes occurring at their mouth (e.g., Amazon) do not develop a delta. The degree of salt intrusion is seasonally and climatically dependent; however, tidal processes are very important in sediment transport dynamics and morphological evolution within the valley;
• Delta-front Estuaries. This category includes the estuaries found in the portions of
deltas affected by tidal dynamics and/or salt intrusion. The classic example is the
outer Mississippi channels.
Structural Estuaries. Their valleys were formed by neotectonic processes such as faulting' vulcanism, postglacial rebound, isostasy, etc. occurred since the Pleistocene. All the
structural processes that give place to the formation of the valley must be active in the
present time or being occurring from the Pleistocene. Otherwise, since almost all rivers are controlled by structural (e.g., faults) conditions their corresponding estuaries
should all be tectonic. Examples are San Francisco Bay (USA) and Valdivia River (Chile).
Coastal Lagoons (after Kjerfve and Magill 1989 ). Inland water bodies usually oriented
parallel to the coast separated from the sea by a barrier and connected to the ocean
by one or more restricted inlets. In the present classification we included the subdivision suggested by Kjerfve and Magill (1989) based on the nature of the entrance:
• Choked: only one long and narrow entrance (Dos Patos, Brazil; Mar Chiquita, Argentina);
• Restricted: few inlets or a wide mouth (Pamlico Sound, USA; San Sebastian Bay, Argentina, Terminos, Mexico);
• Leaky: large number of entrances separated by small barrier islands (Belize Lagoon,
Mississippi Sound).
However, we introduce here a modification for the choked type in two subtypes
depending on the length of the inlet and named short-inlet and long-inlet choked lagoons. The difference is due to the damping effect that has the inlet on the propagation of the tidal wave. Long inlets are more prone to become occluded and eventually
closed (see Knoppers and Kjerfve, this book, for examples of tidal choking and the
damping effects of inlets in Brazilian coastal lagoons).
1.2
World Estuary Distribution
Estuaries are one of the most common features in the world coast. The economical
activities and biological diversity found in estuaries make over 80% of the corresponding values of the coasts. They are subject to more environmental impact and human
influence than beaches or other coastal environments.
A view of the better studied estuaries that there are along the world coasts is given
in Fig. 1.3. The figure provides a geographical demonstration of how much work on
estuaries has spread out. However, in analyzing the degree of knowledge that exist in
every estuary listed in the map, the differences are significant. Whereas, those estuar-
Gerardo M.E. Perillo· M. Cintia Piccolo . Mario Pino-Quivira
mally these estuaries are associated to large discharge rivers that either by their
coastal setting (e.g., de la Plata River) or the relatively strong coastal dynamical
processes occurring at their mouth (e.g., Amazon) do not develop a delta. The degree of salt intrusion is seasonally and climatically dependent; however, tidal processes are very important in sediment transport dynamics and morphological evolution within the valley;
• Delta-front Estuaries. This category includes the estuaries found in the portions of
deltas affected by tidal dynamics and/or salt intrusion. The classic example is the
outer Mississippi channels.
Structural Estuaries. Their valleys were formed by neotectonic processes such as faulting' vulcanism, postglacial rebound, isostasy, etc. occurred since the Pleistocene. All the
structural processes that give place to the formation of the valley must be active in the
present time or being occurring from the Pleistocene. Otherwise, since almost all rivers are controlled by structural (e.g., faults) conditions their corresponding estuaries
should all be tectonic. Examples are San Francisco Bay (USA) and Valdivia River (Chile).
Coastal Lagoons (after Kjerfve and Magill 1989 ). Inland water bodies usually oriented
parallel to the coast separated from the sea by a barrier and connected to the ocean
by one or more restricted inlets. In the present classification we included the subdivision suggested by Kjerfve and Magill (1989) based on the nature of the entrance:
• Choked: only one long and narrow entrance (Dos Patos, Brazil; Mar Chiquita, Argentina);
• Restricted: few inlets or a wide mouth (Pamlico Sound, USA; San Sebastian Bay, Argentina, Terminos, Mexico);
• Leaky: large number of entrances separated by small barrier islands (Belize Lagoon,
Mississippi Sound).
However, we introduce here a modification for the choked type in two subtypes
depending on the length of the inlet and named short-inlet and long-inlet choked lagoons. The difference is due to the damping effect that has the inlet on the propagation of the tidal wave. Long inlets are more prone to become occluded and eventually
closed (see Knoppers and Kjerfve, this book, for examples of tidal choking and the
damping effects of inlets in Brazilian coastal lagoons).
1.2
World Estuary Distribution
Estuaries are one of the most common features in the world coast. The economical
activities and biological diversity found in estuaries make over 80% of the corresponding values of the coasts. They are subject to more environmental impact and human
influence than beaches or other coastal environments.
A view of the better studied estuaries that there are along the world coasts is given
in Fig. 1.3. The figure provides a geographical demonstration of how much work on
estuaries has spread out. However, in analyzing the degree of knowledge that exist in
every estuary listed in the map, the differences are significant. Whereas, those estuar-