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34-603: The rivers mouth bar have moved to disconnect the river from the sea several times in history, for example, after the 2010 Chile earthquake and then again since January 19, 2023. This last change in bar morphology was a consequence of a storm surge . By January 28 a ditch had been made to reconnect the river to the sea. Governor of Valpraíso Region Rodrigo Mundaca criticized however the fact that works were carried out without permission. Low discharge rates caused by excessive uptakes of water in Maipo River have been credited for

68-431: A flat or gently ascending back, which are also called as “Gilbert-type” mouth bars, commonly in deep-water areas of the delta . Lateral spreading of turbulent jet enhanced by increasing frictional resistance in shallow inshore waters, also associated with high bed load, produces almost triangular “middle ground bar” in the mouth of the river causing the channel to bifurcate. As progradation continues, new bars develop at

102-497: A strategic location for the research projects regarding estuarine and delta restoration which makes them ideal for studying the effects of river sediment reduction and relative sea level rise and for estimating the evolution, including land loss and inundation, of the river deltas. A serious example is the Mississippi River Delta where coastal wetlands are disappearing at a rate of approximately 1% of land per year. On

136-452: Is an element of a deltaic system, which refers to the typically mid-channel deposition of the sediment transported by the river channel at the river mouth . River mouth bars form because the cross-sectional area of the expanding sediment-laden outflow increases, and consequently, the sediment transport rate down the jet centerline decreases basinward as flow progresses from confined to unconfined. More specifically, four stages of

170-417: Is converted into runoff in a drainage basin (catchment area or watershed). More precisely, it produces a surface runoff hydrograph in response to a rainfall event, represented by and input as a hyetograph . Rainfall-runoff models need to be calibrated before they can be used. A well known runoff model is the linear reservoir , but in practice it has limited applicability. This hydrology article

204-581: Is exacerbated by surface runoff, leading to a number of down stream impacts, including nutrient pollution that causes eutrophication . Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization . Impervious surfaces ( roads , parking lots and sidewalks ) are constructed during land development . During rain , storms, and other precipitation events, these surfaces (built from materials such as asphalt and concrete ), along with rooftops , carry polluted stormwater to storm drains , instead of allowing

238-562: Is extremely significant within the coastal landscape. Most of the time, they are subaqueous and inaccessible. However, after they emerge and their subaerial portion becomes visible, they evolve into deltaic islands. Consequently, by promoting land expansion, they restore artificially modified shorelines and mitigate coastal erosion , protect coastal communities, promote vegetation growth, provide habitat for rich and productive estuarine ecosystems, and potentially be utilized for farming, living and engineering. Moreover, mouth bar deposits offer

272-528: Is referred to as surface runoff or overland flow . Once in a watercourse , runoff is referred to as streamflow , channel runoff , or river runoff . Urban runoff is surface runoff created by urbanization . The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth . The mass of water on Earth remains fairly constant over time. However,

306-411: Is to understand the dynamics of river mouth bars and the physics behind their formation for future discussions of new land development, estuary restoration, as well as mitigation measures for loss of deltaic wetlands. Runoff (hydrology) Runoff is the flow of water across the earth, and is a major component in the hydrological cycle . Runoff that flows over land before reaching a watercourse

340-540: The Pacific Ocean , near the locality of Llolleo, south of the port of San Antonio . This Santiago Metropolitan Region location article is a stub . You can help Misplaced Pages by expanding it . This Valparaíso Region location article is a stub . You can help Misplaced Pages by expanding it . This article related to a river in Chile is a stub . You can help Misplaced Pages by expanding it . Mouth bar A mouth bar

374-505: The geologic record . Analyses of the hydraulic and sedimentologic conditions of river mouth bar formation, progradation and aggradation , and prediction on their shape, size and spacing are incredibly valuable for reservoir prediction. Eventually, in estuarine regions, there is a mutual interaction between morphology and flow dynamics. While mouth bar morphology is shaped and affected by flow and sediment dynamics or wave and current patterns, mouth bars also modify those dynamics and change

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408-403: The soil . This can occur when the soil is saturated by water to its full capacity, and the rain arrives more quickly than the soil can absorb it. Surface runoff often occurs because impervious areas (such as roofs and pavement ) do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or human-made processes. Surface runoff is a major component of

442-496: The water cycle . It is the primary agent of soil erosion by water . The land area producing runoff that drains to a common point is called a drainage basin . Runoff that occurs on the ground surface before reaching a channel can be a nonpoint source of pollution , as it can carry human-made contaminants or natural forms of pollution (such as rotting leaves). Human-made contaminants in runoff include petroleum , pesticides , fertilizers and others. Much agricultural pollution

476-529: The Earth, through processes including erosion and sedimentation . The water cycle is also essential for the maintenance of most life and ecosystems on the planet. Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to channel runoff (or stream flow ). It occurs when excess rainwater , stormwater , meltwater , or other sources, can no longer sufficiently rapidly infiltrate in

510-660: The Mississippi Delta, in order to eliminate land loss and mitigate coastal erosion, artificial diversions, reconnecting river to the deltaic wetland , have been constructed. Essentially, these diversions are expected to generate mouth bars at downstream end. Therefore, the restoration plans and studies by many scientists and engineers aim ultimately to promote mouth bar deposition by strategically selecting diversion sites and diversion geometries, and consequently stabilizing jet, enhancing bottom friction and sediment trapping efficiencies. This example shows how extremely essential

544-535: The bar top; (4) Finally, as the levees continue to grow and spread due to the presence of the bar, increased water and sediment discharges around the bar cause widening and creation of a classic triangular river mouth bar in plan view. Sediment erosion and deposition dynamics in estuarine region, consequently the formation and growth of mouth bars, are affected by several natural and artificial factors. Human activities, such as reservoir construction, large-scale reclamation and embankment construction completely disturb

578-441: The bar, and subsequently, this acceleration changes the sediment transport gradient over the bar triggering erosion on the upstream bar face and deposition in the downstream bar wake ; (3) River mouth bar progradation stops and it stagnates when depth over the bar is shallow enough to create a fluid pressure on the upstream side of the bar forcing flow around the bar, and consequently decreasing velocity and shear stress over

612-607: The channel flow due to initial mouth bar formation forms new distributary channels and they extend as the mouth bar migrates. Lateral and upstream growth of mouth bar reduces the flow velocity and sediment flux, i.e., flow capacity to carry sediments, through that channel resulting in filling and abandonment of the terminal distributary channel. The active channel, where the flow is diverted into, bifurcates again, following formation of another mouth bar, and creates another unit of channels. Moreover, river mouth bars are important hydrocarbon reservoirs , and have been widely interpreted in

646-429: The delta. Mississippi delta is composed of widely separated buoyancy-dominated mouth bar types in the south ( Southwest Pass and South Pass). Powerful and persistent wave energy and corresponding processes such as wave reworking, refraction of outflow, mixing due to wave breaking , longshore and cross-shore dispersion of sediment generate regular, commonly sand-filled, crescentic bars located at short distances from

680-478: The development of distinct mouth bar morphologies. River discharge , tides and waves can also simultaneously affect the outflow dynamics depending on buoyancy, which play an important role on the evolution of mouth bars. When a river-dominated delta is considered, formation and evolution of terminal distributary channels of the delta, which are the most active parts of the distributive channel network, are closely related to mouth bar formation. Bifurcation of

714-402: The environment. These heat exchanges influence the climate system . The evaporative phase of the cycle purifies water because it causes salts and other solids picked up during the cycle to be left behind. The condensation phase in the atmosphere replenishes the land with freshwater. The flow of liquid water and ice transports minerals across the globe. It also reshapes the geological features of

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748-686: The hydrodynamic balance of the system and permanently interfere with the morphology of mouth bars. Moreover, hydrodynamic factors such as water runoff , discharge fluctuations of the rivers, i.e., non-uniform flow conditions linked to the river hydrograph , sediment flux, sediment characteristics, river mouth geometry, vegetation, existence of tides and waves, play a vital role in sediment erosion and deposition dynamics at river mouths and activate serious geomorphologic controls on mouth bar development. Regarding sediment characteristics, mass and cohesiveness play important roles in river mouth bar evolution. Since coarser sediments are not well suspended by

782-806: The inability of the river to break naturally through the bar in January 2023. In its upper course the river runs as an entrenched torrent through the Andes mountains. Here, it receives three major tributaries: the El Volcán River , the Yeso River and the Colorado River . After leaving the Andes, the Maipo flows through the valley that bears its name, which is one of the principal wine-producing region in Chile. The Maipo River travels 250 km (160 mi) before emptying into

816-408: The jet, they are likely to deposit close to the river mouth and lead to mouth bar construction. On the other hand, since fine sediments are generally transported in a suspended form, they can be carried further and disperse widely, and most of the time, lead to levee construction. Moreover, sediment cohesion, and similarly vegetation , play a role in the morphology of river mouth deposits by enhancing

850-580: The morphology of estuaries. Therefore, the understanding of mouth bar evolution is key for further and better quantification of the changes in river hydraulics and morphodynamics due to mouth bar existence. Mouth bars are categorized based on the primary forces dominating their formation: (1) outflow inertia, (2) turbulent bed friction, (3) effluent buoyancy , (4) wave-induced, and finally, (5) tidal forces. Processes linked to high outflow velocities at deep water outlet and dispersion of sediment due to turbulent jet produce narrow, elongated lunate bars with

884-477: The mouth. The shape and location of the mouth bar also changes with normal or oblique wave incidence. The development of tidal-dominated river mouth bars highly depends on the bidirectional sediment transport by tidal currents causing significant upstream return of sediment into channel. Flood and ebb-dominated sediment transports generate a broad, discontinuous, radial mouth bar dominated by large tidal ridges separated by deep channels. River mouth bar evolution

918-451: The mouths of the bifurcated channels and enhance basinward the delta growth. Mississippi Delta is composed of shallow-water friction-dominated types in the east (Northeast Pass). Dominance of buoyancy processes at the river mouth associated with strong outflow density stratification and fine-grained sediment load rather than bed load , produces laterally restricted, narrow radial bars with gently dipping slopes in shallow water areas of

952-407: The other hand, depend on the relative strength of river inertia with respect to the tidal energy. When tidal energy is much higher than the fluvial one, hydrodynamics of the jet exiting the river mouth, dominating the sediment deposition, are highly affected. Continuously altered tidal wave velocity, width of spreading jet, water depth, and therefore, bottom friction throughout the tidal cycle, cause

986-474: The partitioning of the water into the major reservoirs of ice , fresh water , salt water and atmospheric water is variable and depends on climatic variables . The water moves from one reservoir to another, such as from river to ocean , or from the ocean to the atmosphere. The processes that drive these movements are evaporation , transpiration , condensation , precipitation , sublimation , infiltration , surface runoff , and subsurface flow. In doing so,

1020-478: The river mouth bar formation are: (1) Turbulent jet, expanding into a shallow and sloping basin, first creates parallel subaqueous levees extending basinward and starting a river mouth bar basinward of the levee tips due to the decrease in jet momentum flux and resulting the high sedimentation rate in this region; (2) The subaqueous levees extend basinward and the river mouth bar aggrades and progrades since its presence causes flow acceleration on streamlines over

1054-435: The river mouth bar. In addition to the controls related to fluvial processes , the effects of marine controls, such as wave activity and tides, on river mouths are significant on the mouth bar evolution. Waves have a double effect on mouth bar growth; while small and locally generated waves favor the bar formation by increasing the jet spreading, large, swell waves suppress bar development. The complex effects of tides, on

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1088-440: The stabilization, consequently changing the hydraulic geometry of the mouth and altering the hydrodynamics of the jet. Grain size , which controls the settling velocity of the particles, also influences the location of the river mouth bar basinward of the outlet. In addition, model results recently suggest that river channel width, depth, outflow velocity, and basin slope are the most important variables influencing distance to

1122-399: The water goes through different forms: liquid, solid ( ice ) and vapor . The ocean plays a key role in the water cycle as it is the source of 86% of global evaporation. The water cycle involves the exchange of energy, which leads to temperature changes. When water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms

1156-518: The water to percolate through soil . This causes lowering of the water table (because groundwater recharge is lessened) and flooding since the amount of water that remains on the surface is greater. Most municipal storm sewer systems discharge untreated stormwater to streams , rivers , and bays . This excess water can also make its way into people's properties through basement backups and seepage through building wall and floors. A runoff models or rainfall-runoff model describes how rainfall

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