Sedimentary budgets are a coastal management tool used to analyze and describe the different sediment inputs (sources) and outputs (sinks) on the coasts, which is used to predict morphological change in any particular coastline over time. Within a coastal environment the rate of change of

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

is dependent on the amount of sediment brought into the system versus the amount of sediment that leaves the system. These inputs and outputs of sediment then equate to the total balance of the system and more than often reflect the amounts of

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

or accretion affecting the morphology of the coast.Masselink, G & Hughes, M, 2003, ''Introduction to coastal processes and geomorphology'', Hodder Headline Group, London, pg. 11-14 To assess the sedimentary budget the coast has to be divided into two separate morphologies, commonly known as littoral cells and compartments. Sediment compartments can usually be defined as two rocky barriers which mark the ends of a beach and have a fixed sediment budget, although usually leaky to some extent. Littoral cells can either be free or fixed and can occupy a hierarchy of scales, from individual rip cells to entire beaches.Woodroffe, C, 2003, ''Coasts: form, process and evolution'', Cambridge University Press, UK There are various types of natural sources and sinks within a coastal system. Sediment sources can include river transport, sea cliff erosion and

longshore drift Longshore drift from longshore current is a geological process that consists of the transportation of sediments (clay, silt, pebbles, sand, shingle, shells) along a coast parallel to the shoreline, which is dependent on the angle of incoming w ...

into an area. Sediment sinks can include longshore drift of sediment away from an area and sediment deposition into an

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

. Anthropogenic activities can also influence sedimentary budgets; in particular damming of a river and in stream gravel mining of a river bed can reduce the sediment source to the coast. In contrast

beach nourishment Beach nourishment (also referred to as beach renourishment, beach replenishment, or sand replenishment) describes a process by which sediment, usually sand, lost through longshore drift or erosion is replaced from other sources. A wider beach c ...

can increase sediment source. In 1966, Bowen and Inman defined a littoral cell and separated sediment inputs, accretion by longshore drift and outputs. Sedimentary budgets are used to assist in the management of beach erosion by trying to show the present sediment movement and forecast future sediment movement.List, Jeffrey H. (2005) "Sedimentary budget" in Schwartz, Maurice L. (e.d.) ''Encyclopedia of Coastal Science'' (Encyclopedia of Earth Sciences Series)

Springer Springer or springers may refer to: Publishers * Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag. ** Springer Nature, a multinationa ...

The Netherlands pages 846-850

Feedback mechanisms

In order to understand the sedimentary budget of a coastal environment it is important to know the different types of feedback that can determine whether there is stability. When a beach environment is effected by wind, wave and tidal energy it responds with either positive or negative feedback which determines whether the system is balanced and in

equilibrium Equilibrium may refer to: Film and television * ''Equilibrium'' (film), a 2002 science fiction film * '' The Story of Three Loves'', also known as ''Equilibrium'', a 1953 romantic anthology film * "Equilibrium" (''seaQuest 2032'') * ''Equilibr ...

Negative feedback Negative feedback (or balancing feedback) occurs when some function (Mathematics), function of the output of a system, process, or mechanism is feedback, fed back in a manner that tends to reduce the fluctuations in the output, whether caused ...

is a stabilising mechanism acting to oppose changes to coastal morphology and establish equilibrium. A coastal environment in equilibrium is able to dissipate or reflect incoming energy without the occurrence of sediment input or output and change to morphology. For example; when a beach in equilibrium erodes during a storm it forms an offshore bar that in turn forces waves to break over it. By doing this the waves lose a lot of energy and dissipate before reaching the shoreline, significantly reducing further erosion. When the storm calms, the bar is then re-worked back on to the beach. In contrast

positive feedback Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop where the outcome of a process reinforces the inciting process to build momentum. As such, these forces can exacerbate the effects ...

pushes a coastal system away from equilibrium by modifying its morphology until a threshold is reached, whereby a different type of response occurs. For example; if a storm event was to breach the foredune of a beach that is not in equilibrium, a vulnerable area would be created, which in turn would become susceptible to the formation of a blowout due to wind exploiting the absence of vegetation.

Sediment compartments and littoral cells

Compartmentalisation of the shore occurs where there are major obstacles or objects, especially headlands on deeply embayed coasts. The beaches that are the most enclosed are commonly known as pocket beaches. On these types of beaches the volume of sand remains constant and are closed compartments. Littoral cells can be defined as sediment within a coast that is circulated e.g. rip currents. Littoral cells usually develop on coast which are not impeded by headlands and where longshore currents are allowed to develop. Identifying littoral cells is crucial to determine the sediment budget of sandy coasts. In south-west Western Australia, large

cuspate foreland Cuspate forelands, also known as cuspate barriers or nesses in Britain, are geographical features found on coastlines and lakeshores that are created primarily by longshore drift.Craig-Smith, S. J., Cuspate Forelands. In: M. L. Schwartz, ed. 2005 ...

s and rocky headlands are thought to be boundaries for littoral cells. Boundaries of littoral cells have been defined using tracer studies of sediment movement, geomorphological observation and sedimentological description, heavy mineral sourcing, and analysis of the spatial distribution of wave flux along the shore. Littoral cells are usually an area where changes in the volume of sediment directly affects changes in the coastline, and ideally they are defined to minimise longshore sediment exchange with other littoral cells, for example, a pocket beach surrounded by rocky headlands (which are presumed to exclude sediments). Sub-cells are usually defined to better measure the sediment budget of a coast with varying rates of accretion and erosion. The landward boundary of a littoral cell is usually the foot of a dune or cliff, however, the seaward boundary is difficult to define as mechanisms of

sediment transport Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems wh ...

here are poorly understood. There are three kinds of boundaries between littoral cells: longshore, landward, and seaward; across which sediment may enter the littoral cell or leave it by various processes. It is important to identify which processes operate on a particular littoral cell and also important to identify sediment sources and sinks, as by measuring the sediment gained or lost by these sources and sinks, a sediment budget can be determined.

Sources

Rivers

Rivers are major point sources of sediment contribution to the coastal sedimentary budget, this being particularly true of coasts with a steep gradient, where rivers directly dump their sediments at the coast. Coasts with a low gradient may lose river sediment to estuaries. Sediment delivery to the shoreline can be very intermittent mostly occurring during floods with the increase in flow typically creating an increase in sediment supplied to the coast. Some rivers are referred to as ‘large’ because they produce high amounts of sediment for which to nourish the coastal environment. For example, the Waimakariri River on the coast of

Canterbury Canterbury (, ) is a City status in the United Kingdom, city and UNESCO World Heritage Site, in the county of Kent, England; it was a county borough until 1974. It lies on the River Stour, Kent, River Stour. The city has a mild oceanic climat ...

, New Zealand produces 77% of sediment supplied to the

Pegasus Bay Pegasus Bay, earlier known as Cook's Mistake, is a bay on the east coast of the South Island of New Zealand, to the north of Banks Peninsula. Toponymy Pegasus Bay takes its name from the brig ''Pegasus'', a sealing ship that was sailing from H ...

coastline. This is not always the case with some rivers referred to as ‘small’ because they struggle to supply enough sediment to keep their coastlines from eroding, for example, the

Rakaia River The Rakaia River is in the Canterbury Plains in New Zealand's South Island. The Rakaia River is one of the largest braided rivers in New Zealand. The Rakaia River has a mean flow of and a mean annual seven-day low flow of . In the 1850s, Europ ...

South of

Banks Peninsula Banks Peninsula () is a rocky peninsula on the east coast of the South Island of New Zealand that was formed by two now-extinct volcanoes. It has an area of approximately . It includes two large deep-water harbours — Lyttelton Harbour a ...

in Canterbury, New Zealand. The construction of river dams for flood control and

hydropower Hydropower (from Ancient Greek -, "water"), also known as water power or water energy, is the use of falling or fast-running water to Electricity generation, produce electricity or to power machines. This is achieved by energy transformation, ...

reduces sediment supply to many coastlines due to the trapping of sediment and the decrease in flood peaks and flood intensity. In places such as

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...

of the United States, in particular the San Luis Rey River, dams are built to control flooding of properties along the river. Ironically, in doing so, this is contributing to the damage of coastal properties due to a lack of sediment produced to protect the beaches.Kondolf, G, 1997,”Hungry Water: Effects of Dams and Gravel Mining on River Channels”, ''Environmental Management'', vol.21, no.4, pp.533-551. Another example is the

Aswan Dam The Aswan Dam, or Aswan High Dam, is one of the world's largest embankment dams, which was built across the Nile in Aswan, Egypt, between 1960 and 1970. When it was completed, it was the tallest earthen dam in the world, surpassing the Chatuge D ...

constructed on the

Nile River The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the longest river i ...

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

in 1964. Prior to the construction of the Aswan Dam, the Nile River delivered 60-180 million tonnes of sediment and water to the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

every year. Sediment supply is now almost zero which has produced a significant imbalance to the near shore sedimentary budget, creating major erosion and shifting of sediment along the coast. The effects of sediment trapping due to dams can be exacerbated when combined with other activities such as in-stream gravel mining. Excavation of gravel from a river bed forms pits within the channel profile which can trap much of the incoming

bed load The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load. Bed load moves by rolling, sliding, and/or Saltation (geolo ...

sediment, preventing or slowing it from reaching the coastline. Mining can also reducing the amount of overall sediment available for transport, especially when it occurs down stream from dams. For example; approximately 300,000m³ of gravel is extracted from the San Luis Rey River in South California every year, which is almost 50 times more than the bedload sediment yield after the dam was built. Thus, removing more bedload sediment further decreases the sediment yield available to the coast. The removal of natural vegetation for cultivation and land use can increase soil erosion resulting in an increase in sediment yield transported by rivers to the coast. For example; in Westland New Zealand this has had a cumulative effect with clear felling of trees increasing in river sediment yield up to eight times.

Sea cliff erosion

Sea cliff erosion is a large source of sediment to many coastal sedimentary budgets, initiated by many different processes including wave attack, rainfall and groundwater seepage. Cliff erosion can be influenced by rising sea levels and is magnified with

storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the ...

events. An example of cliff erosion is the erosion of large

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to Semi-arid climate, semiar ...

s that span the length of the Canterbury Bight, situated north of the

Waitaki River The Waitaki River is a large braided river in the South Island of New Zealand. It drains the Mackenzie Basin and runs south-east to enter the Pacific Ocean between Timaru and Oamaru on the east coast. It starts at the confluence of the Ōhau Ri ...

in New Zealand. The erosion of these cliffs, due to high energy wave environments contributes 70% of the overall material supplied to these beaches.Hart D, Marsden I, Francis M. 2008. Chapter 20: Coastal Systems. In: Winterbourne, M, Knox, G.A. Marsden, I.D., Burrows, C (eds.) ''Natural History of Canterbury'' (3rd edn). Canterbury University Press, 30p, pp 653-684

Storms

Although less frequently observed than river transport and sea cliff erosion, storms may account for a large percentage of coastal sedimentary budgets. Following

Hurricane Katrina Hurricane Katrina was a powerful, devastating and historic tropical cyclone that caused 1,392 fatalities and damages estimated at $125 billion in late August 2005, particularly in the city of New Orleans and its surrounding area. ...

and

Hurricane Rita Hurricane Rita was the most intense tropical cyclone on record in the Gulf of Mexico, tying with Hurricane Milton in 2024 Atlantic hurricane season, 2024, as well as being the fourth-most intense Atlantic hurricane ever recorded. Part of the ...

in 2005, over 131 x 10⁶ metric tons of sediment were deposited along the Louisiana and eastern Texas Gulf Coast. Study of the western Louisiana coastal wetlands found hurricanes appear to be the "overwhelming pathway" by which sediment is deposited in that location, accounting for amounts of sediment far greater than amounts deposited by the local river systems.Turner, R. Eugene, et al. "Wetland sedimentation from hurricanes Katrina and Rita." ''Science'' 314.5798 (2006): 449-452. Based annualized estimates of magnitude of sediment deposition, hurricanes have been found to deposit hundreds of times more sediment in these coastal wetland regions than man-made river diversions intended to redirect river-transported sediment to starving wetland systems. For salt marsh wetlands, particularly those of coastal Louisiana, sediment accumulation from hurricanes is "sufficient" to account for the entire inorganic sedimentary budget.

Sinks

Estuaries

Estuaries are an example of a coastal sink in that they tend to trap sediment which can be due to tidal circulations and the mixing of fresh and salt water, the injection of river sediment and the presence of

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

s. As the tide rises and falls water and sediment is pumped into the estuary. Because salt water and sediment particles are heavier than fresh water they tend to be carried the bottom until the sediment sinks to the floor and is trapped within the estuary. The movement of sands and offshore material into an estuary generally depends on the direction of longshore drift and the movement of bottom waters across the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

. Estuaries can often trap a lot of coarse bedload sediments that are fed down rivers, intercepting them before they reach the coast. The

North Island The North Island ( , 'the fish of Māui', historically New Ulster) is one of the two main islands of New Zealand, islands of New Zealand, separated from the larger but less populous South Island by Cook Strait. With an area of , it is the List ...

of New Zealand experiences sediment sinks into estuaries often, enhanced by the presence of mangroves. Mangroves are sediment hungry and trap a lot of suspended sediment with their complex aerial

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

structure, thus functioning as land builders.

Aeolian transport

Sand that is blown by the wind inland to form sand dunes usually develop on shorelines where there is suitably strong winds. This can be a major sink for the sediment budget of a shoreline.

Longshore drift

Longshore drift of sediment is important for distributing sediment along the coast, and is considered one of the most important mechanisms. The longshore drift of sediment can be considered both a source and a sink due to the fact that in some case it can add sediment to a coastline but in others transport sediment away from a coastline. An example of both extremes of longshore drift can be found on the Canterbury coastline in New Zealand, either side of Banks Peninsular. Both the Waimakariri River in the north and the Canterbury Bight in the south of the Banks Peninsula provide large amounts of sediment respectively. The difference is the sediment supplied by the Waimakariri River is a source for the coast's New Brighton spit due to the reversal of southern currents transporting sediment to the south. In contrast the Canterbury Bight has a combination of high energy environments and strong southern longshore currents that transport large amounts of sediment north, which can be classified as a sink, putting a deficit to the coasts sedimentary budget. As a result, there is erosion of the Canterbury Bight and a predominantly balanced New Brighton Spit. Models have been developed for measuring longshore drift which can assist in determining a sedimentary budget, if they are integrated over the correct timescale. The sediment budget takes into consideration sediment sources and sinks within a

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

. This sediment can come from any source with examples of sources and sinks consisting of: *

River A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s *

Lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

s * Eroding land sources * Artificial sources e.g. nourishment * Artificial sinks e.g. mining/extraction * Offshore transport * Deposition of sediment on shore This sediment then enters the coastal system and is transported by longshore drift. A good example of the sediment budget and longshore drift working together in the coastal system is

inlet An inlet is a typically long and narrow indentation of a shoreline such as a small arm, cove, bay, sound, fjord, lagoon or marsh, that leads to an enclosed larger body of water such as a lake, estuary, gulf or marginal sea. Overview In ...

ebb-tidal shoals, which store sand that has been transported by long shore transport. As well as storing sand these systems may also transfer or by pass sand into other beach systems, therefore inlet ebb-tidal

shoal In oceanography, geomorphology, and Earth science, geoscience, a shoal is a natural submerged ridge, bank (geography), bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body ...

systems provide a good sources and sinks for the sediment budget.

Cross-shore movement

Wave

swash Swash, or forewash in geography, is a turbulent layer of water that washes up on the beach after an incoming wave has broken. The swash action can move beach materials up and down the beach, which results in the cross-shore sediment exchange. T ...

and currents can impact significantly on the sediment budget, although it is difficult to measure. Swash can be either an erosive or accretion process depending on many factors such as the sand texture and the individual wave itself. Although during fair weather the impact of swash is negligible, during storms the sea level can rise high enough to erode dunes and cliffs, dumping large quantities of sediment into the littoral cell, which can only be given back to the dune by aeolian transport. Where storm surge causes sediments to be deposited on the land from the littoral cell, they can form washover fans or open a new tidal inlet which transports sediment away from the littoral cell.

Management

Coastal nourishment

When a coastal environment is in sediment deficit,

anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Anthropogenic may also refer to things that have been generated by humans, as follows: * Human impact on the enviro ...

sediment nourishment is one way in which a balanced sedimentary budget can be maintained. This type of

coastal erosion Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along the coastline due to the action of Wind wave, waves, Ocean current, currents, tides, wind-driven water, waterborne ice, or other impacts ...

management has been adopted all over the world in order to preserve and protect. An example of this is at

Mount Maunganui Mount Maunganui (, ) is a major residential, commercial and industrial suburb of Tauranga located on a peninsula to the north-east of Tauranga's city centre. It was an independent town from Tauranga until the completion of the Tauranga Harb ...

beach in the North Island of New Zealand which had been experiencing erosion, resulting in coastal dune retreat of almost 20m. When ongoing dredging at the entrance to the Tauranga Harbour began, it was decided that the sediment removed would be used to re-nourish the Mt. Manganui beach. The sediment was deposited in the nearshore zone promoting beach accretion by offshore berm emplacement. Results show that most of the 80,000m³ of sediment added to the nearshore zone made it to ashore to re-nourish the beach and even out the past sediment deficit. Nourishment of a coast can be regarded as a fast fix option to reversing a sediment deficit; however, it is important that nourishment is on-going in order to ensure the sedimentary budget remains balanced.

Coastal protection

When protecting the coastline it is important to understand how the sedimentary budget can be affected when implementing appropriate coastal protecting techniques. Often management plans for coastal erosion have seen the use of ‘hard’ engineering structures as a means of protecting the coastline from recession. In particular

groyne A groyne (in the U.S. groin) is a rigid aquatic structure built perpendicularly from an ocean shore (in coastal engineering) or a river bank, interrupting water flow and limiting the movement of sediment. It is usually made out of wood, concrete ...

s which are used to trap the longshore drift of sediment that often deprives a beach. Groynes have the ability to change the coast's sediment budget, accreting up drift beaches but at the same time starving down drift beaches. This management approach is not used so much these days, with modern knowledge of coastal dynamics promoting the use of ‘soft’, natural approaches such as nourishment and preservation of natural systems such as dunes.

Coastal planning

Being able to incorporate the sedimentary budget into a coastal management plan is becoming critical, especially in today's world where the majority of populations are living and owning property very close to the coast. One of the essential components drawn from sediment budget is being able to predict the morphological change that is likely to occur to a coastline over time, especially when creating plans associated with major environmental change such as sea level rise. Incorporating a sediment budget into a coastal plan has been recognised as highly important in the

Hawke's Bay Hawke's Bay () is a region on the east coast of New Zealand's North Island. The region is named for Hawke Bay, which was named in honour of Edward Hawke. The region's main centres are the cities of Napier and Hastings, while the more rural ...

of New Zealand for finding information relating to

hazard A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would potentially allow them to cause damage to health, life, property, or any other interest of value. The probability of that ...

zones, beach property protection, and coastal erosion as well as assess the successfulness of current management strategies.Komar, P, 2005, “Hawke’s Bay, New Zealand: Environmental Change, Shoreline Erosion and Management Issues”, Report for Hawke’s Bay Regional Council. The major setback with using the sediment budget for management and what is probably the underlining issue regarding the sediment budget is its complexity.