Daily Flood Peak

 The term 'Daily Flood Peak' as it applies to the area of the weather can be defined as ' In hydrologic terms, the maximum mean daily discharge occurring in a stream during a given flood event'.

 


Dam

 A barrier constructed to hold back water and raise its level, forming a reservoir used to generate electricity or as a water supply.


Dam Failure

 A dam is a barrier across flowing water that obstructs, directs or slows down the flow, often creating a reservoir, lake or impoundments. Most dams have a section called a spillway or weir over which, or through which, water flows, either intermittently or continuously, and some have hydroelectric power generation systems installed.

 

Dampers

 A damper is a valve or plate that stops or regulates the flow of air inside a duct, chimney, VAV box, air handler, or other air handling equipment. A damper may be used to cut off central air conditioning (heating or cooling) to an unused room, or to regulate it for room-by-room temperature and climate control. Its operation can be manual or automatic. Manual dampers are turned by a handle on the outside of a duct. Automatic dampers are used to regulate airflow constantly and are operated by electric or pneumatic motors, in turn controlled by a thermostat or building automation system. Automatic or motorized dampers may also be controlled by a solenoid, and the degree of air-flow calibrated, perhaps according to signals from the thermostat going to the actuator of the damper in order to modulate the flow of air-conditioned air in order to effect climate control.

 

DCP (Data Collection Platform

 An electronic device that connects to a river or rainfall gage that records data from the gage and at pre-determined times transmits that data through a satellite to a remote computer.


Dead End

 The end of a water main, which is not connected to other parts of the distribution system.


Dead Storage

 The Volume in a reservoir below the lowest controllable level


Debris

 organic material (Leaves, twigs, etc.) and sediment.


Decomposition

 Is the process by which organic substances are broken down into a much simpler form of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death. Animals, such as worms, also help decompose the organic materials. Organisms that do this are known as decomposers. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy from the Greek word taphos, meaning tomb.

 

Deep Percolation Loss

 Water that percolates below the lower limit of the Root Zone of plants into a ground water aquifer and cannot be used by plants.

 

Deforestation

Deforestation implies the long-term or permanent loss of forest cover and implies transformation into another land use. Such a loss can only be caused and maintained by a continued human-induced or natural perturbation.



Delta

 A river delta is a landform that forms at the mouth of a river, where the river flows into an ocean, sea, estuary, lake, or reservoir. Deltas form from deposition of sediment carried by a river as the flow leaves its mouth. Over long periods, this deposition builds the characteristic geographic pattern of a river delta. 


Dendrites

 Crystal that develops with a typical multi-branching tree-like form.


Denuded Land

In geology, denudation is the long-term sum of processes that cause the wearing away of the Earth’s surface leading to a reduction in elevation and relief of landforms and landscapes. Endogenous processes such as volcanoes, earthquakes, and plate tectonics uplift and expose continental crust to the exogenous denudation processes of weathering, erosion, and mass wasting.


Desalination

 Desalination (desal) is the process of removing dissolved salts and minerals from seawater or brackish water. It is also called desalting or by its shortened name, desal. Desalination produces drinking water and concentrate (the water that contains the salts that were removed in the desalination process, which is sometimes called brine). The dominant technology used in desalination today is reverse osmosis, which involves forcing water through semi-permeable membranes to remove salts and other impurities. 


Desertification

 Desertification defind as "land degradation in arid, semi-arid and dry subhumid areas resulting from various factors, including climatic variations and human activities". 


Diagenesis

 Diagenesis  is the change of sediments or existing sedimentary rocks into a different sedimentary rock during and after rock formation (lithification), at temperatures and pressures less than that required for the formation of metamorphic rocks. It does not include changes from weathering. It is any chemical, physical, or biological change undergone by a sediment after its initial deposition, after its lithification. This process excludes surface alteration (weathering) and metamorphism. These changes happen at relatively low temperatures and pressures and result in changes to the rock's original mineralogy and texture. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures than the former. Hydrothermal solutions, meteoric groundwater, porosity, permeability, solubility, and time are all influential factors. 


Diesel

A petroleum-based fuel which is burned in engines ignited by compression rather than spark; commonly used for heavy duty engines including buses and trucks.
diesel engine - an internal combustion engine that uses diesel as fuel, producing harmful fumes.


Dioxin A man-made chemical by-product formed during the manufacturing of other chemicals and during incineration. Studies show that dioxin is the most potent animal carcinogen ever tested, as well as the cause of severe weight loss, liver problems, kidney problems, birth defects, and death.

Drainage Area

 The total land area where surface water runs off and collects in a stream or series of streams that make up a single watershed.


Dredging

 Dredging is the removal of sediments and debris from the bottom of lakes, rivers, harbors, and other water bodies. It is a routine necessity in waterways around the world because sedimentation the natural process of sand and silt washing downstream gradually fills channels and harbors.


Dump sites

Waste disposal grounds.


Dune Stabilization

 Dunes are a natural coastal feature on moderately exposed and exposed coasts. Dunes are formed by the sand, which blows inland from the beach and is deposited in the area behind the coastline.