HOME

TheInfoList




Surface runoff (also known as overland flow) is the flow of
water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , even though it provide ...

water
occurring on the ground surface when excess
rainwater Rain is liquid water in the form of Drop (liquid), droplets that have condensation, condensed from atmosphere, atmospheric water vapor and then precipitation (meteorology), become heavy enough to fall under gravity. Rain is a major component ...

rainwater
,
stormwater entering a storm drain A storm drain, storm sewer (United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a ...
,
meltwater Meltwater is water released by the melting of snow or ice, including glaciers, glacial ice, tabular icebergs and ice shelf, ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reduci ...
, or other sources, can no longer sufficiently rapidly infiltrate in the
soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms tha ...

soil
. This can occur when the
soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms tha ...

soil
is saturated by water to its full capacity, and that the rain arrives more quickly than the soil can absorb it. Surface runoff often occurs because
impervious Permeability in fluid mechanics and the Earth sciences (commonly symbolized as ''k'') is a measure of the ability of a porous media, porous material (often, a Rock (geology), rock or an unconsolidated material) to allow fluids to pass through it. ...
areas (such as
roof A roof is the top covering of a , including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against , , , extremes of , and . A roof is part of the . The characteristic ...

roof
s and pavement) do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or man-made processes. Surface runoff is a major component of the
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, describes the continuous movement of water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, ...

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 A drainage basin is any area of land where precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheric science is the study of the Earth's atmosphere File:Atmosphere gas proportions.svg, Compos ...

drainage basin
. Runoff that occurs on the ground surface before reaching a
channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austr ...
can be a
nonpoint source of pollution
nonpoint source of pollution
, as it can carry man-made contaminants or natural forms of pollution (such as rotting leaves). Man-made contaminants in runoff include
petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

petroleum
,
pesticide Pesticides are substances that are meant to control pest (organism), pests. The term pesticide includes all of the following: herbicide, insecticides (which may include insect growth regulators, termiticides, etc.) nematicide, molluscicide, pi ...
s,
fertilizer A fertilizer (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American En ...

fertilizer
s and others. In addition to causing water erosion and pollution, surface runoff in urban areas is a primary cause of urban flooding, which can result in property damage, damp and mold in
basements A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the boiler, water heating, water heate ...
, and street flooding.


Generation

Surface runoff is defined as
precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mod ...

precipitation
(rain, snow, sleet, or hail) that reaches a surface stream without ever passing below the soil surface. It is distinct from direct runoff, which is runoff that reaches surface streams immediately after rainfall or melting snowfall and excludes runoff generated by the melting of
snowpack Snowpack forms from layers of snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of f ...
or glaciers.
Snow Snow comprises individual ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). ...
and
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
melt occur only in areas cold enough for these to form permanently. Typically
snowmelt In hydrology Hydrology (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...
will peak in the spring and glacier melt in the summer, leading to pronounced flow maxima in rivers affected by them. The determining factor of the rate of melting of snow or glaciers is both air temperature and the duration of sunlight. In high mountain regions, streams frequently rise on sunny days and fall on cloudy ones for this reason. In areas where there is no snow, runoff will come from rainfall. However, not all rainfall will produce runoff because storage from soils can absorb light showers. On the extremely ancient soils of
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
and
Southern Africa Southern Africa is the south South is one of the cardinal directions or compass points. South is the opposite of north and is perpendicular to the east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Pr ...
,
proteoid root Proteoid roots of ''Leucospermum cordifolium'' Cluster roots, also known as proteoid roots, are plant roots that form clusters of closely spaced short lateral rootlets. They may form a two- to five-centimetre-thick mat just beneath the leaf litter. ...
s with their extremely dense networks of root hairs can absorb so much rainwater as to prevent runoff even when substantial amounts of rain fall. In these regions, even on less infertile
cracking clay soils
cracking clay soils
, high amounts of rainfall and potential evaporation are needed to generate any surface runoff, leading to specialised adaptations to extremely variable (usually ephemeral) streams.


Infiltration excess overland flow

This occurs when the rate of
rainfall Rain is liquid water in the form of droplet Raindrops in a plant. A drop or droplet is a small column of liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechani ...

rainfall
on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. This is also called Hortonian overland flow (after Robert E. Horton), or unsaturated overland flow. This more commonly occurs in
arid A region is arid when it is characterized by a severe lack of available water, to the extent of hindering or preventing the growth and development Development or developing may refer to: Arts *Development hell, when a project is stuck in d ...

arid
and
semi-arid A semi-arid climate, semi-desert climate, or steppe climate is the climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables ove ...
regions, where rainfall intensities are high and the
soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms tha ...

soil
infiltration capacity Infiltration is the process by which water on the ground surface enters the soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_c ...
is reduced because of
surface sealingSoil sealing or soil surface sealing is the loss of soil resources due to the covering of land for housing, road A road is a thoroughfare, route, or way on land between two Location (geography), places that has been Pavement (material), paved o ...
, or in urban areas where pavements prevent water from infiltrating.


Saturation excess overland flow

When the
soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms tha ...

soil
is saturated and the depression storage filled, and rain continues to fall, the rainfall will immediately produce surface runoff. The level of antecedent soil moisture is one factor affecting the time until soil becomes saturated. This runoff is called saturation excess overland flow, saturated overland flow, or Dunne runoff.


Antecedent soil moisture

Soil retains a degree of moisture after a
rainfall Rain is liquid water in the form of droplet Raindrops in a plant. A drop or droplet is a small column of liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechani ...

rainfall
. This residual water moisture affects the soil's
infiltration capacity Infiltration is the process by which water on the ground surface enters the soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_c ...
. During the next rainfall event, the infiltration capacity will cause the soil to be saturated at a different rate. The higher the level of antecedent soil moisture, the more quickly the soil becomes saturated. Once the soil is saturated, runoff occurs. Therefore, surface runoff is a significantly factor in the controlling of soil moisture after medium and low intensity storms.


Subsurface return flow

After water infiltrates the soil on an up-slope portion of a hill, the water may flow laterally through the soil, and exfiltrate (flow out of the soil) closer to a channel. This is called subsurface return flow or
throughflowIn hydrology Hydrology (from Greek: wikt:ὕδωρ, ὕδωρ, "hýdōr" meaning "water" and wikt:λόγος, λόγος, "lógos" meaning "study") is the scientific study of the movement, distribution, and management of water on Earth and other p ...
. As it flows, the amount of runoff may be reduced in a number of possible ways: a small portion of it may ; water may become temporarily stored in microtopographic depressions; and a portion of it may infiltrate as it flows overland. Any remaining surface water eventually flows into a
receiving water Receiving may refer to: * ''Kabbalah'', "receiving" in Hebrew * Receiving department (or receiving dock), in a distribution center * Receiving house, a theater * Receiving line, in a wedding reception * Receiving mark, postmark * sexual penetratio ...
body such as a
river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

river
,
lake A lake is an area filled with water, localized in a basin, surrounded by land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is situated at elevations above sea level (variable ove ...

lake
,
estuary An estuary is a partially enclosed Coast, 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 envir ...

estuary
or
ocean The ocean (also the sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
.


Human influence

Urbanization Urbanization (or urbanisation) refers to the population shift from rural File:Rural landscape in Finland.jpg, A rural landscape in Lappeenranta, South Karelia, Finland. 15 July 2000. In general, a rural area or a countryside is a geographi ...
increases surface runoff by creating more
impervious surface s are highly impervious. Impervious surfaces are mainly artificial structures—such as Pavement (material), pavements (road A road is a thoroughfare, route, or way on land between two Location (geography), places that has been Pavement (materia ...
s such as pavement and buildings that do not allow
percolation Fig. 2: Percolation in a square lattice (Click to animate) In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ...

percolation
of the water down through the soil to the
aquifer An aquifer is an underground layer of -bearing , rock fractures or unconsolidated materials (, , or ). can be extracted using a water . The study of water flow in aquifers and the characterization of aquifers is called . Related terms include a ...

aquifer
. It is instead forced directly into streams or , where
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
and
siltation Siltation, is water pollution Water pollution (or aquatic pollution) is the contamination of water bodies ( Lysefjord) in Norway Norway ( nb, ; nn, ; se, Norga; smj, Vuodna; sma, Nöörje), officially the Kingdom of Norway, is ...
can be major problems, even when flooding is not. Increased runoff reduces
groundwater Groundwater is the water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known form ...

groundwater
recharge, thus lowering the
water table The water table is the upper surface of the Phreatic zone, zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is ...

water table
and making
drought A drought is an event of prolonged shortages in the water supply, whether atmospheric (below-average precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheric science is the study of the Earth's atm ...

drought
s worse, especially for agricultural farmers and others who depend on the
water well A well is an excavation or structure created in the ground by digging Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surf ...

water well
s. When anthropogenic contaminants are dissolved or suspended in runoff, the human impact is expanded to create
water pollution Water pollution (or aquatic pollution) is the contamination of , usually as a result of human activities, in such a manner that negatively affects its legitimate uses. Water pollution reduces the ability of the body of water to provide the tha ...

water pollution
. This pollutant load can reach various receiving waters such as streams, rivers, lakes, estuaries and oceans with resultant water chemistry changes to these water systems and their related ecosystems. A 2008 report by the
United States National Research Council The National Academies of Sciences, Engineering, and Medicine (also known as NASEM or the National Academies) is the collective scientific national academy A national academy is an organizational body, usually operating with state financial sup ...
identified urban stormwater as a leading source of
water quality Water quality refers to the Chemical property, chemical, Physical property, physical, and Biology, biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against whi ...

water quality
problems in the U.S. As humans continue to alter the climate through the addition of
greenhouse gases A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature' ...

greenhouse gases
to the atmosphere, precipitation patterns are expected to change as the atmospheric capacity for water vapor increases. This will have direct consequences on runoff amounts.


Effects of surface runoff


Erosion and deposition

Surface runoff can cause
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
of the Earth's surface; may be deposited a considerable distance away. There are four main types of soil erosion by water: splash erosion, sheet erosion,
rill In hillslope geomorphology, a rill is a shallow Channel (geography), channel (no more than a few tens of centimetres deep) cut into soil by the erosion, erosive action of Overland flow, flowing water. Similar but smaller incised channels are kno ...
erosion and
gully A gully is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the scien ...

gully
erosion. Splash erosion is the result of mechanical collision of raindrops with the soil surface: soil particles which are dislodged by the impact then move with the surface runoff. Sheet erosion is the overland transport of
sediment Sediment is a naturally occurring material that is broken down by processes of weathering Weathering is the deterioration of rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is cate ...

sediment
by runoff without a well defined channel. Soil surface roughness causes may cause runoff to become concentrated into narrower flow paths: as these incise, the small but well-defined channels which are formed are known as
rill In hillslope geomorphology, a rill is a shallow Channel (geography), channel (no more than a few tens of centimetres deep) cut into soil by the erosion, erosive action of Overland flow, flowing water. Similar but smaller incised channels are kno ...
s. These channels can be as small as one centimeter wide or as large as several meters. If runoff continue to incise and enlarge rills, they may eventually grow to become
gullies A gully is a landform created by running water, erosion, eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width. When the gully formation is in pr ...

gullies
. Gully erosion can transport large amounts of eroded material in a small time period. Reduced crop productivity usually results from erosion, and these effects are studied in the field of
soil conservation Soil conservation is the prevention of loss of the top most layer of the soil from erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from ...
. The soil particles carried in runoff vary in size from about .001 millimeter to 1.0 millimeter in diameter. Larger particles settle over short transport distances, whereas small particles can be carried over long distances suspended in the
water column A water column is a concept Concepts are defined as abstract ideas A mental representation (or cognitive representation), in philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind ...
. Erosion of silty soils that contain smaller particles generates
turbidity Turbidity is the cloudiness or haziness of a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (matter), phase of matter ...

turbidity
and diminishes light transmission, which disrupts
aquatic ecosystem An aquatic ecosystem is an ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles a ...

aquatic ecosystem
s. Entire sections of countries have been rendered unproductive by erosion. On the high central
plateau In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...

plateau
of
Madagascar Madagascar (; mg, Madagasikara), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), and previously known as the Malagasy Republic The Malagasy Republic ( mg, Repoblika Mala ...

Madagascar
, approximately ten percent of that country's land area, virtually the entire landscape is devoid of
vegetation Vegetation is an assemblage of plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular re ...

vegetation
, with erosive gully furrows typically in excess of 50 meters deep and one kilometer wide.
Shifting cultivation Shifting cultivation is an agricultural Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated ...

Shifting cultivation
is a farming system which sometimes incorporates the
slash and burn Slash-and-burn agriculture is a farming method that involves the cutting and burning of plants in a forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating ...
method in some regions of the world. Erosion causes loss of the fertile top soil and reduces its fertility and quality of the agricultural produce. Modern industrial
farming Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors suc ...

farming
is another major cause of erosion. Over a third of the U.S.
Corn Belt The Corn Belt is a region of the Midwestern United States The midwestern United States, often referred to simply as the Midwest, is one of four Census Bureau Region, census regions of the United States Census Bureau (also known as "Region ...

Corn Belt
has completely lost its
topsoil Topsoil is the upper, outermost layer of soil, usually the top . It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biology, biological soil activity occurs. Topsoil is composed of mineral partic ...
. Switching to
no-till No-till farming (also known as zero tillage or direct drilling) is an agricultural technique for growing crops or pasture without disturbing the soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''C ...
practices would reduce soil erosion from U.S. agricultural fields by more than 70 percent.


Environmental effects

The principal environmental issues associated with runoff are the impacts to surface water,
groundwater Groundwater is the water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known form ...

groundwater
and
soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms tha ...

soil
through transport of water pollutants to these systems. Ultimately these consequences translate into human health risk, ecosystem disturbance and aesthetic impact to water resources. Some of the contaminants that create the greatest impact to surface waters arising from runoff are
petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

petroleum
substances,
herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control unwanted plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, conv ...
s and
fertilizer A fertilizer (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American En ...

fertilizer
s. Quantitative uptake by surface runoff of pesticides and other contaminants has been studied since the 1960s, and early on contact of pesticides with water was known to enhance
phytotoxicity Phytotoxicity is a toxic effect by a compound on plant Plants are mainly multicellular organisms, predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energ ...
. In the case of surface waters, the impacts translate to
water pollution Water pollution (or aquatic pollution) is the contamination of , usually as a result of human activities, in such a manner that negatively affects its legitimate uses. Water pollution reduces the ability of the body of water to provide the tha ...

water pollution
, since the streams and rivers have received runoff carrying various chemicals or sediments. When surface waters are used as
potable water Drinking water, also known as potable water, is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main ...

potable water
supplies, they can be compromised regarding and drinking water
aesthetics Aesthetics, or esthetics (), is a branch of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about existence Existence is the ability of an entity to interact with physical reality R ...

aesthetics
(that is, odor, color and
turbidity Turbidity is the cloudiness or haziness of a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (matter), phase of matter ...

turbidity
effects). Contaminated surface waters risk altering the metabolic processes of the aquatic
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
that they host; these alterations can lead to death, such as
fish kill The term fish kill, known also as fish die-off, refers to a localized die-off of fish populations which may also be associated with more generalized mortality of aquatic life.University of Florida. Gainesville, FL (2005) ''Plant Management in Flo ...
s, or alter the balance of populations present. Other specific impacts are on animal mating, spawning,
egg An egg is the organic vessel containing the in which an develops until it can survive on its own, at which point the animal hatches. An egg results from of an . Most s, (excluding s), and lay eggs, although some, such as s, do not. eg ...
and
larva A larva (plural larvae ) is a distinct juvenile form many animal Animals (also called Metazoa) are organisms that form the Animalia. With few exceptions, animals , , are , can , and grow from a hollow sphere of , the , during . Ove ...
e viability, juvenile survival and plant productivity. Some researches show surface runoff of pesticides, such as
DDT Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless Crystallinity, crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmen ...

DDT
, can alter the gender of fish species genetically, which transforms male into female fish. Surface runoff occurring within forests can supply lakes with high loads of mineral nitrogen and phosphorus leading to
eutrophication Eutrophication (from Greek ''eutrophos'', "well-nourished") is the process by which an entire body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmå ...

eutrophication
. Runoff waters within
coniferous forests A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing and ecological function. The Food and Agricult ...
are also enriched with
humic acid Humic substances are organic compounds that are important components of humus, the major organic compound, organic fraction of soil, peat, and coal (and also a constituent of many upland river, streams, dystrophic lakes, and ocean water). For a long ...

humic acid
s and can lead to
humification In soil science, humus (derived in 1790–1800 from the Latin for 'earth, ground') denominates the fraction of soil organic matter that is amorphous and without the "cellular cake structure characteristic of plants, micro-organisms or animals". ...

humification
of water bodies Additionally, high standing and young islands in the tropics and subtropics can undergo high soil erosion rates and also contribute large material fluxes to the coastal ocean. Such land derived runoff of sediment nutrients, carbon, and contaminants can have large impacts on global
biogeochemical cycle In ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Topics of interest include the bi ...
s and marine and coastal ecosystems. In the case of groundwater, the main issue is contamination of drinking water, if the
aquifer An aquifer is an underground layer of -bearing , rock fractures or unconsolidated materials (, , or ). can be extracted using a water . The study of water flow in aquifers and the characterization of aquifers is called . Related terms include a ...

aquifer
is abstracted for human use. Regarding
soil contamination 280px, Excavation showing soil contamination at a disused gasworks in England. Soil contamination or soil pollution as part of land degradation is caused by the presence of xenobiotics (human-made) chemicals or other alteration in the natural soil ...
, runoff waters can have two important pathways of concern. Firstly, runoff water can extract soil contaminants and carry them in the form of water pollution to even more sensitive aquatic habitats. Secondly, runoff can deposit contaminants on pristine soils, creating health or ecological consequences.


Agricultural issues

The other context of agricultural issues involves the transport of agricultural chemicals (nitrates, phosphates, pesticides, herbicides, etc.) via surface runoff. This result occurs when chemical use is excessive or poorly timed with respect to high precipitation. The resulting contaminated runoff represents not only a waste of agricultural chemicals, but also an environmental threat to downstream ecosystems. Pine straws are often used to protect soil from soil erosion and weed growth. However, harvesting these crops may result in the increase of soil erosion.


Economic Issues.

Surface run-off results in a significant amount of economic effects. Pine straws are cost effective ways of dealing with surface run-off. Moreover, Surface run-off can be reused through the growth of elephant mass. In
Nigeria Nigeria (), officially the Federal Republic of Nigeria, is a country in West Africa West Africa or Western Africa is the westernmost region of . The defines Western Africa as the 17 countries of , , , , , , , , , , , , , , , and as we ...

Nigeria
,
elephant grassThe term Elephant grass may refer to the following grass species: * The Asian '' Miscanthus giganteus'', also known as giant miscanthus, commonly used as a biomass crop * The African ''Pennisetum purpureum'', also known as napier grass, Uganda grass ...

elephant grass
is considered to be an economical way in which surface run-off and
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
can be reduced. Also,
China China (), officially the People's Republic of China (PRC; ), is a country in . It is the world's , with a of more than 1.4 billion. China spans five geographical and 14 different countries, the in the world after . Covering an area of ap ...

China
has suffered significant impact from surface run-off to most of their economical crops such as vegetables. Therefore, they are known to have implemented a system which reduced loss of nutrients ( nitrogen and phosphorus) in soil.


Flooding

Flood A flood is an overflow of water that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the . Floods are an area of study of the discipline and are of significant concern in , a ...

Flood
ing occurs when a watercourse is unable to convey the quantity of runoff flowing downstream. The frequency with which this occurs is described by a
return periodA return period, also known as a recurrence interval or repeat interval, is an average time or an estimated average time between events such as earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface o ...
. Flooding is a natural process, which maintains ecosystem composition and processes, but it can also be altered by
land use Land use involves the management and modification of natural environment or wilderness Wilderness or wildlands (usually in the plural), are natural environments on Earth that have not been significantly modified by human activity or any nonur ...
changes such as river engineering. Floods can be both beneficial to societies or cause damage. Agriculture along the
Nile The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Saharan languages, Nilo-Saharan language family. "Nobiin" is the genitive case, genitive form of ''Nòòbíí'' ("Nub ...

Nile
floodplain took advantage of the seasonal flooding that deposited nutrients beneficial for crops. However, as the number and susceptibility of settlements increase, flooding increasingly becomes a natural hazard. In urban areas, surface runoff is the primary cause of urban flooding, known for its repetitive and costly impact on communities. Adverse impacts span loss of life, property damage, contamination of water supplies, loss of crops, and social dislocation and temporary homelessness. Floods are among the most devastating of natural disasters. The use of is also recognized as a significant way in which crops such as maize can retain in soil, resulting in improvement of crop water availability.


Mitigation and treatment

Mitigation of adverse impacts of runoff can take several forms: *
Land use Land use involves the management and modification of natural environment or wilderness Wilderness or wildlands (usually in the plural), are natural environments on Earth that have not been significantly modified by human activity or any nonur ...
development controls aimed at minimizing
impervious surface s are highly impervious. Impervious surfaces are mainly artificial structures—such as Pavement (material), pavements (road A road is a thoroughfare, route, or way on land between two Location (geography), places that has been Pavement (materia ...
s in urban areas *
Erosion control Erosion control is the practice of preventing or controlling wind or water erosion In earth science, erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved ...
s for
farm A farm (also called an agricultural Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases i ...

farm
s and
construction Construction is a general term meaning the and to form , , or ,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and comes from ''constructio'' (from ''com-' ...

construction
sites * Flood control and retrofit programs, such as
green infrastructure Green infrastructure or blue-green infrastructure refers to a network that provides the “ingredients” for solving urban and climatic challenges by building with nature.Hiltrud Pötz & Pierre Bleuze (2011). Urban green-blue grids for sustainable ...
* Chemical use and handling controls in
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...

agriculture
,
landscape maintenance 200px, One example of a maintained landscape from Beaverton, Oregon Landscape maintenance (or groundskeeping) is the art and vocation of keeping a landscape healthy, clean, safe and attractive, typically in a garden, yard (land), yard, park, in ...
, industrial use, etc. Land use controls. Many world regulatory agencies have encouraged research on methods of minimizing total surface runoff by avoiding unnecessary
hardscape Hardscape refers to hard landscape materials in the built environment In urban planning, architecture and civil engineering, the term built environment, or built world, refers to the human impact on the environment, human-made environment that ...
. Many municipalities have produced guidelines and codes (
zoning Zoning is a method of urban planning Urban planning, also known as regional planning, town planning, city planning, or rural planning, is a technical and political process that is focused on the development and design of land use and the bu ...
and related ordinances) for land developers that encourage minimum width sidewalks, use of paving stone (flooring), pavers set in earth for driveways and walkways and other design techniques to allow maximum water infiltration (hydrology), infiltration in urban settings. An example land use control program can be seen in the city of Santa Monica, California. Erosion controls have appeared since medieval times when farmers realized the importance of contour farming to protect soil resources. Beginning in the 1950s these agricultural methods became increasingly more sophisticated. In the 1960s some U.S. state, state and local governments began to focus their efforts on mitigation of construction runoff by requiring builders to implement erosion control, erosion and sediment controls (ESCs). This included such techniques as: use of straw bales and barriers to slow runoff on slopes, installation of silt fences, programming construction for months that have less rainfall and minimizing extent and duration of exposed graded areas. Montgomery County, Maryland, Montgomery County, Maryland implemented the first local government sediment control program in 1965, and this was followed by a statewide program in Maryland in 1970. Flood control programs as early as the first half of the twentieth century became quantitative in predicting peak flows of riverine systems. Progressively strategies have been developed to minimize peak flows and also to reduce channel velocities. Some of the techniques commonly applied are: provision of holding ponds (also called detention basins or balancing lakes) to buffer riverine peak flows, use of energy dissipators in channels to reduce stream velocity and land use controls to minimize runoff. Chemical use and handling. Following enactment of the U.S. Resource Conservation and Recovery Act (RCRA) in 1976, and later the Clean Water Act, Water Quality Act of 1987, states and cities have become more vigilant in controlling the containment and storage of toxic chemicals, thus preventing releases and leakage. Methods commonly applied are: requirements for double containment of underground storage tanks, registration of hazardous materials usage, reduction in numbers of allowed pesticides and more stringent regulation of fertilizers and herbicides in landscape maintenance. In many industrial cases, pretreatment of wastes is required, to minimize escape of pollutants into sanitary sewer, sanitary or storm sewer, stormwater sewers. The U.S. Clean Water Act (CWA) requires that local governments in urbanized areas (as defined by the Census Bureau) obtain
stormwater entering a storm drain A storm drain, storm sewer (United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a ...
discharge permits for their drainage systems. Essentially this means that the locality must operate a Stormwater#Stormwater management, stormwater management program for all surface runoff that enters the municipal separate storm sewer system ("MS4"). EPA and state regulations and related publications outline six basic components that each local program must contain: * Public education (informing individuals, households, businesses about ways to avoid stormwater pollution) * Public involvement (support public participation in implementation of local programs) * Illicit discharge detection & elimination (removing sanitary sewer or other non-stormwater connections to the MS4) * Construction site runoff controls (i.e. erosion & sediment controls) * Post-construction (i.e. permanent) stormwater management controls * Pollution prevention and "good housekeeping" measures (e.g. system maintenance). Other property owners which operate storm drain systems similar to municipalities, such as state highway systems, universities, military bases and prisons, are also subject to the MS4 permit requirements.


Measurement and mathematical modeling

Runoff is analyzed by using mathematical models in combination with various
water quality Water quality refers to the Chemical property, chemical, Physical property, physical, and Biology, biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against whi ...

water quality
sampling methods. Measurements can be made using continuous automated water quality analysis instruments targeted on pollutants such as specific organic compound, organic or inorganic chemicals, pH, turbidity etc. or targeted on secondary indicators such as dissolved oxygen. Measurements can also be made in batch form by extracting a single water sample and conducting any number of chemical or physical tests on that sample. In the 1950s or earlier hydrology transport models appeared to calculate quantities of runoff, primarily for flood forecasting. Beginning in the early 1970s computer models were developed to analyze the transport of runoff carrying water pollutants, which considered Solvation, dissolution rates of various chemicals, Infiltration (hydrology), infiltration into soils and ultimate pollutant load delivered to surface water, receiving waters. One of the earliest models addressing chemical dissolution in runoff and resulting transport was developed in the early 1970s under contract to the United States Environmental Protection Agency (EPA). This computer model formed the basis of much of the mitigation study that led to strategies for
land use Land use involves the management and modification of natural environment or wilderness Wilderness or wildlands (usually in the plural), are natural environments on Earth that have not been significantly modified by human activity or any nonur ...
and chemical handling controls. Increasingly, stormwater practitioners have recognized the need for Monte Carlo models to simulate stormwater processes because of natural variations in multiple variables that affect the quality and quantity of runofff. The benefit of the Monte Carlo analysis is not to decrease uncertainty in the input statistics, but to represent the different combinations of the variables that determine potential risks of water-quality excursions. One example of this type of stormwater model is the ''stochastic empirical loading and dilution model'' (''SELDM'')Granato, G.E., 2013, Stochastic empirical loading and dilution model (SELDM) version 1.0.0: U.S. Geological Survey Techniques and Methods, book 4, chap. C3, 112 p. http://pubs.usgs.gov/tm/04/c03/ is a
stormwater entering a storm drain A storm drain, storm sewer (United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use Britain as a ...
quality model. SELDM is designed to transform complex scientific data into meaningful information about the risk of adverse effects of runoff on receiving waters, the potential need for mitigation measures, and the potential effectiveness of such management measures for reducing these risks. SELDM provides a method for rapid assessment of information that is otherwise difficult or impossible to obtain because it models the interactions among hydrologic variables (with different probability distributions) that result in a population of values that represent likely long-term outcomes from runoff processes and the potential effects of different mitigation measures. SELDM also provides the means for rapidly doing sensitivity analyses to determine the potential effects of different input assumptions on the risks for water-quality excursions. Other computer models have been developed (such as the DSSAM Model) that allow surface runoff to be tracked through a river course as reactive water pollutants. In this case the surface runoff may be considered to be a line source of
water pollution Water pollution (or aquatic pollution) is the contamination of , usually as a result of human activities, in such a manner that negatively affects its legitimate uses. Water pollution reduces the ability of the body of water to provide the tha ...

water pollution
to the receiving waters.C.M.Hogan, Marc Papineau et al. ''Development of a dynamic water quality simulation model for the Truckee River'', Earth Metrics Inc., Environmental Protection Agency Technology Series, Washington D.C. (1987)


See also

* * * *Flash flood * * * – U.S. Research program * * * * * * * * * * *


References


Further reading

*Gebert, W. A., D.J. Graczyk, and W.R. Krug. (1987). ''Average annual runoff in the United States, 1951-80'' [Hydrologic Investigations Atlas HA-710]. Reston, Va.: U.S. Department of the Interior, U.S. Geological Survey. * Shodor Education Foundation (1998
"Surface Water Runoff Modeling."


External links

*USDA NRCS National Engineering Handbook
Stage Discharge Relationships, Ch. 14NutrientNet
an online nutrient trading tool developed b
the World Resources Institute
designed to address water quality issues related to surface runoff and other pollution. See also th
PA NutrientNet
website designed for Pennsylvania's nutrient trading program.
Bioretention
as a Low-impact development (Canada/US), low impact development method of treating surface runoff * * *
Stormwater Model
USGS Stochastic Empirical Loading and Dilution Model (SELDM) {{Rivers, streams and springs Aquatic ecology Earth phenomena Environmental chemistry Soil erosion Hydrology Irrigation Soil contamination Water pollution Ocean pollution