Glossary

Here you can find descriptions of difficult words that are used throughout the course.

A

• Abiotic conditions = non-living physical, chemical and geomorphological forces and interactions within an ecosystem.
• Accretion/accrete = deposition and subsequent increase of the sediment at a particular site.
• Adaptability = generally, the ability of a system to determine its behavior according to changes in the environment or in the system itself. For engineering design, an adaptable structure is future-proof, because potential future changes have been taken into account in its design.
• Anoxic sediments = sediments depleted of oxygen.

B

• Banks = land alongside of a water body (river, estuary, lake or sea).
• Barrier = an obstacle that prevents the passage of something; in the course, it is often used to refer to infrastructures that impede the passage of water or sediments.
• Bending moment = internal reaction of a structure to external forces causing the element to bend.
• Berm = an elevated barrier that separates two areas. 
• Biodiversity = a measure of the variety of organisms present in different ecosystems. Involves variability within and between species and between ecosystems.
• Biogeomorphology = study of the interactions between organisms and the development of landforms.
• Biotope = area of uniform physical and chemical (in)organic conditions where communities can establish. 
• Boundary condition = condition that is required to be satisfied at all or part of the boundary of a region in which a set of differential conditions is to be solved. (source: Oxford Dictionary)
• Breakwater = a coastal barrier that is built parallel or perpendicular to the coast line; functions to protect coastal region against currents, waves and accretion of sand.

C

• Canal/Channel = artificial open or closed waterway.
• Clay = material that is often present in estuaries and river regions; grain size diameter varies from 1 μm to 4 μm.
• Compaction = a process that occurs when soil is packed together; in other words, as a result of loading, the empty spaces between soil particles is reduced.
• Cost-benefit analysis = analysis to evaluate the monetary value of a project when both, costs and benefits, are considered.
• Crest = top of the dike.

D

• Dam = a barrier that prevents water from flowing from one side of the barrier to the other side of the barrier. The accumulation of water on one side of the barrier typically forms a reservoir.
• Diaphragm wall = vertical wall inside a dike to prevent seepage (slow passage of water through the openings of the dike as a result of the difference in water levels on both sides of the dike).
• Delft 3D = Delft 3D is an open source 2D and 3D modelling software package developed by Deltares to simulate currents, sediment transport, morphology, waves and water quality, and the interactions between these processes.
• Delta = A landform resulting from the deposition of sediment carried by a river as the flow leaves its mouth and enters another water body. Deltas can vary in size, ranging from those of a small stream to the Yangtze Delta or the Mississippi Delta.
• Dike = a barrier that prevents the passage of water from one side to the other; thus, water is only present on one side.
• Discharge = volume of a fluid (e.g. water) that is released by a certain cross-section per unit of time.
• Dissipation of waves = occurs when waves either break or decrease in height.
• Dowels = cylinder, typically made of wood, plastic or metal, used to guarantee the stability of a dike.
• Dredging = the action of clearing the bed of a harbour, river or estuary by scooping out mud, weeds and rubbish. (source: Oxford dictionary)
• Dune = a natural coastal defence system consisting of sand.

E

• Ebb tide = the movement of water back towards the ocean following high water; this continues until low water is attained.
• Ecological succession = process of change in the species and structure of an ecosystem over time. The time scale can range from years to decades or beyond. Ecological succession begins with few pioneering species. As the complexity of their interactions increases, the ecosystem evolves until it reaches its climax state.
• Ecosystem = a biological community of organisms and their physical environment, which interact as a system. (source: Oxford Dictionary)
• Embankment = water retaining structure made of natural materials (e.g. sand, clay or rock).
• Erosion = a process in which dissolved materials, soil or rock particles are removed from a surface and transported to a different location by the action of water or wind.
• Estuary = body of brackish water (water with higher salinity than freshwater but lower salinity than freshwater) where tide occurs (ebb and flood processes) that results from the mixing of seawater and freshwater or from fossil aquifers.

F

• Failure = collapse that occurs when a structure no longer fulfills its function. When failure occurs, the Ultimate Limit State (ULS) has been reached.
• Failure mechanism = mechanism that can start failure of the structure. There are more than fifty mechanisms in which a dike can fail; however, this MOOC considers macro instability, piping, erosion of outer slope and erosion of inner slope.
• Fetch = length of undisturbed water surface over which wind can blow and waves can develop.
• Fish ladder = a series of pools built like steps in a ladder to enable fish to ascend a dam. (source: Oxford Dictionary)
• Flood tide = the movement of tide on to the beach up until high water is attained.
• Flood defence = a structure that prevents flooding.
• Flooding = the process of water overflowing its usual boundaries; typically, flooding submerges land that is usually dry.
• Flood plain = space on sides of the river that is usually dry during summer and filled with water during winter; storage function.
• Foundation = the load bearing part of a building; normally below ground level.
• Freeboard = additional height to account for wave overtopping and uncertainties.
• Fresh water lens = a fresh water lens is a convex layer of groundwater floating on top of a denser saltwater layer. It is usually formed when rainwater seeps down through sandy sediments.
• Functional requirements = the actions that an infrastructure should be able to perform, or the standards that it should meet. They impose constraints on a design or implementation of a hydraulic structure.

G

• Gate = a hinged barrier used to close an opening in a river, estuary or sea.
• Geohydrology = study of the movement of groundwater through soil, rocks and the Earth’s crust, including aquifers.
• Groundwater = water that is situated between the pores between the grains of the soil.
• Groundwater flow = transport of groundwater through the soil.
• Groyne = hydraulic structures (similar to breakwaters) that are perpendicular to the landside (either coast or river). (source: Oxford Dictionary) In river it functions to keep the river navigable; in a coastal region it protects the beach from structural erosion.

H

• Habitat = area of uniform physical and chemical (in)organic conditions where communities have established. 
• Harbour = in history it was a place of ‘natural’ shelter where ships could be safely anchored. (source: Oxford Dictionary) Used interchangeably with port.
• Hinterland = area located inland of the coast, harbour or river.
• Hydraulic Engineering = discipline that is responsible for designing hydraulic structures for and developing knowledge on coastal, river, and other water concerned regions.
• Hypoxic bottom layer = deep layer of water with low dissolved oxygen concentration.

I

• Implement ability = the ability to implement the project in a specific region.
• (In)organic cycles = pathways by which chemical substances, organic or not, move through the organic and inorganic components of the Earth. Some well-studied cycles include those of Carbon, Nitrogen, Sulfur and Phosphorus.
• Inner berm = mainly used to provide stability; to counteract the movement of the saturated sliding plain on the inner side of a dike.
• Inner dike = region that is protected by a dike, often the dry side of the dike.
• Inner slope = side of the dike that is vulnerable for overtopping.
• Inner slope erosion = failure mechanism in which overtopping has a negative impact on the inner slope of the dike. Erosion occurs and eventually this might lead to a collapse of the dike.
• Inorganic material = material without Carbon e.g. sand (fine to coarse grain sizes) silt, clay and grave.
• Irrigation = artificial way of transporting water serving agriculture.
• Intertidal mudflat = coastal wetlands formed by the deposition of mud from tides or rivers. They usually form in areas such as bays, lagoons or estuaries and are located between the high and low tide levels, experiencing regular submergence and exposure.
• Intertidal zone = area located between the high and low tide levels, experiencing regular submergence and exposure.

J

• Jetty = a landing stage at which boats can dock or be moored. (source: Oxford Dictionary)

K

• Keystone species = a keystone species has a disproportionately large effect on an ecosystem relative to its abundance. It is a crucial species for ecosystem functioning because they determine the distribution and numbers of other species. When a keystone species is missing from the food web, the structure of the ecosystem may change irreversibly.

L

• Lagoon = a shallow body of water, between the coast and the mainland. Often separated from a larger water body by a reef of sand or coral, it usually has a restricted inlet.
• Levee = same/see Dike.
• Life-cycle = a view of a system that addresses all phases of its existence from conception to disposal, aimed at preventing a piecemeal approach.
• Lifetime = the duration of a thing’s existence or usefulness. (source: Oxford Dictionary)
• Limnological = the study of inland waters, both running and standing. The term is commonly used for the study of lake water bodies.
• Load = a weight or source of pressure borne by something. (source: Oxford Dictionary)
• Longshore transport = movement of sediment by water waves and currents along the coast (parallel to the coast).
• Lock = hydraulic structure that serves to separate and connect two different water levels.

M

• Macro instability = failure mechanism in which sliding plain becomes saturated and starts to slide. Eventually this leads to a complete collapse of the dike.
• Maintenance = the process of preserving a condition or situation or the state of being preserved. (source: Oxford Dictionary)
• Mangrove = ecosystem, depending on mangrove trees, at the boundary between ocean, freshwater and land. Only found in tropical and subtropical regions.
• Mitre gate = detail of a storm surge barrier, that can be swung into the river to enclose the river and consists of two elements.
• Multi-criteria analysis (MCA) = an analysis in which an object/project is assessed based on several criteria, these criteria can have different weights.

N

• Nails = method to guarantee the stability of a dike, similar to dowels.
• Navigation = passage of vessels and other type of ships
• Neap-tide = when the sun and moon are 90 degrees out phase the attractive forces decrease, consequently the tide is at its minimum.
• Nearshore zone = the shallow zone of the sea/ocean close to the coast, the permanently submerged zone between the coast and offshore.
• Nourishment = artificial replenishment of sand in coastal region. (source: Oxford Dictionary)

O

• Offshore bar = a ridge of sand built up roughly parallel to the coast in the nearshore zone through the action of tides, currents and waves on the sediments.
• (In)organic cycles = pathways by which chemical substances, organic or not, move through the organic and inorganic components of the Earth. Some well-studied cycles include those of Carbon, Nitrogen, Sulfur and Phosphorus.
• Organic material = material containing Carbon. This can be living material or derive from living material.
• Outer berm = situated on the outer side of a dike (mostly at coast) at similar level as design water level, waves break on this berm.
• Outer dike = region that is not protected by the dike. (source: Oxford Dictionary) Often wet side of the dike.
• Outer slope = side of the dike that is vulnerable for wave impact.
• Outer slope erosion = failure mechanism in which waves or currents have a negative impact on the outer slope of the dike. Erosion occurs and eventually this might lead to a collapse of the dike.
• Overtopping = water that flow over the crest of a dike during storm or high water events.

P

• Permeability = the degree to which water is allowed to pass through the soil.
• Pier = a structure projecting from the shore into the sea used as a landing stage for boats. (source: Oxford Dictionary)
• Pioneer species = the first species to colonize a biotope. These are generally species that are specialized and that can survive harsh conditions.
• Pioneer zone = zone inhabited by pioneer species.
• Piping = failure mechanism internal erosion has created pipes underneath the structure. Water and soil particles are transported out of the structure.
• Piping berm = lower and longer berm on the inner side to reduce the risk of piping; in fact the seepage length is increased.
• Polder = area that is surrounded by water retaining structures; water resource is strictly managed.
• Port = man made places of shelter purpose built for efficient transfer of cargo. (source: Oxford Dictionary) Used interchangeably with harbour.
• Prefab = prefabricated elements that are used at the building side. (source: Oxford Dictionary)

Q

• Quay wall = wall often situated in harbours/ports along which ships can moor and unload. (source: Oxford Dictionary)

R

• Reliability = for engineering, reliability means that the hydraulic structure should continue to function smoothly and well, and should not require many repairs.
• Resilience (ecological) = the capacity of an ecosystem to deal with disturbances and still be able to bounce back to the original healthy ecosystem state. An ecosystem is resilient when it is able to withstand and even benefit from reasonable, foreseeable disturbances.
• Resilience (engineering) = the capacity of the engineering structure to withstand a second shock, or sudden high load, of similar magnitude to the first and yet retain its structural integrity and continue to meet the functional requirements.
• Revetment = retaining sloping structure placed on banks to protect these banks.
• River bed = bottom layer of the river.
• Roller gate = detail of a storm surge barrier, that can be slid into the river to enclose the river.

S

• Safety = the condition of being protected from or unlikely to cause danger, risk, or injury. (source: Oxford Dictionary)
• Salt marsh = coastal wetlands that are flooded by salt water during tidal differences.
• Sand = material that is often present in coastal regions; grain size diameter varies from 64 μm to 2 mm.
• Sand nourishment = artificial supply of sand, from elsewhere, to the shore or beach to combat coastal erosion. May also be used to increase the width of a beach used intensively for recreation. Sand nourishment can occur directly on a beach (using trucks and bulldozers) or via shoreface nourishments using dredgers.
• Saturated soil = all pores in the soil are filled with water, i.e. there is no air present in the soil anymore.
• Scour = removal of underwater material by waves and currents, especially at the base or toe of a shore structure.
• Sea bed = bottom layer of the sea.
• Seepage = groundwater flows underneath a dike as a result of the difference in water levels on both sides of the dike.
• Seepage length = the shortest length a water particle has to travel underneath a dike from one side (high water level) to another (low/no water level).
• Settlement = subsidence (natural process) of the ground as a result, it is a process that needs time.
• Set-up = water level increase as a result of wind blowing over a certain fetch.
• Sheet pile wall = soil- and water retaining structures often made of steel.
• Sliding plain = area in a dike that is vulnerable to become saturated and starts to slide/move; leads to macro instability.
• Slufter = small estuary with a perched inlet. Seawater enters the system during flood tides.
• Sluice = hydraulic structure that retains water on two sides; water can pass underneath.
• Slurry wall = walls (can be made inside a dike) to restrict groundwater flow or support excavations. (source: Oxford Dictionary)
• Spring-tide = tide that rises highest and falls lowest from Mean Sea Level, so the tide with maximum range. This occurs at or near new or full moon, roughly every 14 days, because of gravitational forces.
• Stability = the state of being in balance, after a small disturbance it bounces back to its original state.
• Stakeholders = all parties, individuals and organisations, affected by, interested in, or having power related to, a project.
• Storm surge = high water level as a result of tide (flood) and wind set-up.
• Storm surge barrier = hydraulic structure that prevents the hinterland from flooding.
• Structural integrity = deals with the ability of a structure to support a designed load without failing
• Swinging gate = detail of a storm surge barrier, that can be swung into the river to enclose the river, often curved gates.

T

• Tender = market mechanism were the client searches and selects the contractor.
• Tide = periodical change of water level as a result of the attractive forces between the sun, moon and earth.

V

• Vessel = large ship.

W

• Water board = governmental institution (only in the Netherlands) which is responsible for protecting the land and all small hydraulic infrastructure at a regional scale. (source: Oxford Dictionary)
• Waves = a long body of water curling into an arched form and breaking on the shore. (source: Oxford Dictionary)
• Weir = hydraulic structure that forms a barrier in a river; regulates the water level.
• Wetland = land that is saturated; can be temporarily or permanent.

Z

• Zone integrity = The natural mosaic of the ecosystem is fully represented. The presence of the full range of diversity across the particular area under consideration is a condition for ecosystem health.