Drowned rivers

Rivers transport material in several phases dissolved, suspended particulate and bed load. Physical and chemical processes within an estuary infiuence the transportation and transformation of this material, thereby affecting the net supply of material to the oceans. Several definitions and geomorphologic classifications of estuaries have been reviewed by Pe-rillo (1995). From a chemical perspective, an estuary is most simply described as the mixing zone between river water and seawater characterised by sharp gradients in the ionic strength and chemical composition. Geographic distinctions can be made between drowned river valleys, fjords and bar-built estuaries. They can alternatively be classified in terms of the hydrodynamic regime as ... 

FIGURE 3-8 A flow net for a hypothetical aquifer formed in a drowned river valley, which is assumed to be of uniform thickness over its area and located between two water-impermeable walls of bedrock. The hydraulic head varies between 2 m and 4.9 m. Squares A and B and points x and y are used in Example 3-2. 

In the last ice age, when much of the water of the world s oceans was frozen as ice and sea levels were lower than they are now, the coasdines extended past their present positions. Then, as now, many rivers flowed to the sea, cutting deep, V-shaped valleys as they went. Thousands of years later, when much of the ice caps melted and sea levels rose, water filled in, or drowned, these river troughs. The type of coast that is dominated by an old river valley is called a drowned river, or ria coast (after the Spanish term ria, which means estuary ). The Chesapeake Bay is a good example of this type of coastline. 

Near shore, the interaction between the ocean and coastal rivers results in the formation of fresh-salt water interfaces, known as estuaries. Depending on coastal geology, they can assume various forms, such as fjords, drowned river valleys, or bar-built estuaries, characterized by barrier islands. Tidal effects, storms, and the mixing, or lack thereof, of salt water and freshwater strongly influence the biology... 

Altliough ail accurate assessment could not be tnade itnmediately, tlie Ashland spill look a heavy toll on tlie wildlife of the Ohio River Valley. More tluiii 5000 waterfowl were killed when their feathers became contaminated witli oil. Birds tliat e. perience oil conlaminalion lose tlieir natural insulation and buoyancy and cither drown or freeze to death. In addition, a massive fish kill was e. pectcd in the spring when the ri cr entered a new cycle. 

Raina and her friend went to a popular place for parties along the Eel River in Potter Valley, where they tried methamphetamine that was supplied by a drug dealer. The girls became disoriented, were sexually assaulted, and left the party in a confused state. What happened after that is a mystery, except for the fact that Raina drowned in the river. ... 

River-dominated estuaries are formed in high river discharge regions where the valley is presently not drowned by the sea. The two subcategories are as follows (a) tidal river estuaries are associated with large rivers systems that are influenced by tidal action with the salt front usually not well developed at the mouth (b) delta-front estuaries are found in sections of deltas that are affected by tidal action and/or salt intrusion. 

River-dominated estuary formed in high river discharge regions where the valley is presently not drowned by the sea. 

Some inorganic elements were drawn into plant tissues through their roots from the swamp water and peaty soil this material is known as "inherent" mineral matter (30) in the final coal. Ultimately the swamp was drowned by rivers or sea water from which sand and mud were deposited onto the dying forest. Peats covered with seawater were injected with sulfate, but those covered by thick and impermeable river muds (fresh water) remained more or less free of sulfate. 

Environments ofTerrigenous/Siliciclastic Sedimentation That Are Associated with Mouths of Large Rivers 2,5,1,1,2,1 Estuaries An estuary is a drowned mouth of a river valley forming a funnel-shaped coastal indentation in which seawater can circulate and mix with river freshwater. Estuaries form where the discharged fluvial sedimentary load is small (<16 mg/1), subsidence is greater than sediment accumulation, and in macrotidal zones. Most of the estuaries are located in humid temperate climatic zones where extensive vegetation effectively restricts erosion and riverine sediment transport (Friedman and Sanders, 1978). 

The present-day shelves and their sediments reflect conditions of the Last Glacial period and probably the former low sea level stands at depths of over 100 m. Large bodies of wind-blown, river-transported, and nearshore marine sand that accumulated on the Pleistocene coastal plains, beaches, and river mouths, and were drowned by the Holocene rapid sea-level rise. These sediments are only partially covered by modem sediments, resulting in very complex shelf morphologies. A (near-) equilibrium state between hydraulic processes and sediment distribution in which the shelf has been completely covered... 

On April 27, 1865, the side-wheeler steamer Sultana, overloaded and carrying more passengers than it should, steamed up the Mississippi River. The Sultana carried more than 2,000 Union soldiers, many bound for home after being released from Confederate prison camps. Quick repairs had been made to the vessel s boilers at Memphis. A few miles north of Memphis, the boilers blew up and tore the Sultana apart, hurling men and parts of the vessels hundreds of feet. An estimated 1,700 soldiers died either from the explosion or from drowning. The pressures at which the Sultana s boiler normally operated, and even the pressure at which it ruptured so violently, would be considered low compared with boiler pressures commonly used today. 

There was a man, stone dead, sitting on his bicycle as it leaned against a bridge railing. You could tell that many had gone down to the river to get a drink of water and had died where they lay. I saw a few live people still in the water, knocking against the dead as they floated down the river. There must have been hundreds and thousands who fled to the river to escape the fire and then drowned. 

Summer is here and with it many activities centered around water. Pools, lakes, rivers, or the ocean—all can be a lot of fun, but they can be deadly, too. Did you know that more than 3,000 people accidentally drown every year And while this sobering statistic represents all age groups, children up to the age of four years have the highest death rate. 

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