WATERSHED AND COASTAL DEFINITION

WATERSHED AND COASTAL ZONE RELATIONSHIP AND PROBLEM
Oleh: Syukron Ma’mun

A. Watershed Definition
Etimology : water +‎ shed, a calque of German Wasserscheide, a compound of Wasser (“‘water’”) + Scheide (“‘divide’”).
Terminology : A watershed is an extent of land where water from rain or snow melt drains downhill into a body of water, such as a river, lake, reservoir, estuary, wetland, sea or ocean. The drainage basin includes both the streams and rivers that convey the water as well as the land surfaces from which water drains into those channels, and is separated from adjacent basins by a drainage divide.
The drainage basin acts like a funnel, collecting all the water within the area covered by the basin and channelling it into a waterway. Each drainage basin is separated topographically from adjacent basins by a geographical barrier such as a ridge, hill or mountain, which is known as a water divide.
Other terms that are used to describe a Watershed are catchment, catchment area, catchment basin, drainage area, river basin, and water basin . In the technical sense, a watershed refers to a divide that separates one drainage area from another drainage area. However, in the United States and Canada, the term is often used to mean a drainage basin or catchment area itself. Watersheds drain into other watersheds in a hierarchical pattern, with smaller sub-watersheds combining into larger drainage basins.
The Environmental Protection Agency launched the website, Watershed central for the public to exchange information and locate resources needed to restore local watersheds.
Example of a drainage basin. The dashed line is the main water divide of the hydrographic basin







Homes, farms, ranches, forests, small towns, big cities and more can make up watersheds. Some cross county, state, and even international borders. Watersheds come in all shapes and sizes. Some are millions of square miles, others are just a few acres. Just as creeks drain into rivers, watersheds are nearly always part of a larger watershed. 


B. Coastal zone
Coastal zone is Lands and waters adjacent to the coast that exert an influence on the uses of the sea and its ecology, or whose uses and ecology are affected by the sea. The continental shelf, continental margin, coastal ocean and coastal zone are fuzzy concepts for which various definitions have been proposed.


Extent of the coastal zone. (Source: University of Liverpool)
The continental shelf is the area extending from the coast to the shelf break, which is usually defined by the 200 meter depth isobaths. The continental margin is the transition zone between the continental crust and the oceanic crust, including the coastal plain, continental shelf, slope and rise. The coastal ocean is the portion of the global ocean where physical, biological and biogeochemical processes are directly affected by land. It is either defined as the part of the global ocean covering the continental shelf or the continental margin. The coastal zone usually includes the coastal ocean as well as the portion of the land adjacent to the coast that influences coastal waters. It can readily be appreciated that none of these concepts has a clear operational definition
If the coastal zone is delineated on the basis of the shelf break, it has been established that the average depth of the shelf-slope break is closer to 125 m. The choice makes little difference in terms of the area. The world coastline extends over 350,000-1,000,000 km, depending upon how finely the "length" is resolved. Within its extent, the coastal ocean and the immediately landward region of the coastal zone displays a wide diversity of geomorphologic types and ecosystems.
Despite its relatively modest surface area, the coastal zone plays a considerable role in the biogeochemical cycles because virtually all land-derived materials (water, sediments, dissolved and particulate nutrients, etc.) enter this region in surface runoff or groundwater flow. These terrestrial inputs are changing, largely as a consequence of human influence; about 40% of the world population lives within 100 km of the coastline, and this proportion is increasing. In addition, the coastal ocean exchanges large amounts of matter and energy with the open ocean. As a consequence of these external influences the coastal ocean constitutes one of the most geochemically and biologically active areas of the biosphere. For example, it accounts for at least 15% of oceanic primary production, 80% of organic matter burial, 90% of sedimentary mineralization, 75-90% of the oceanic sink of suspended river load and ca. 50% of the deposition of calcium carbonate. Additionally, it represents 90% of the world fish catch and its overall economic value has been recently estimated as at least 40% of the value of the world's ecosystem services and natural capital.
Despite its potential importance, the coastal ocean has been relatively neglected until recently, probably because of its intrinsic complexity. It is the focus of several national and international ongoing research programs. The Land-Ocean Interactions in the Coastal Zone (LOICZ) program was established as part of the IGBP Global Change Programme (IGBP) in 1993. It is now also a core project of the International Human Dimensions Programme on Global Environmental Change (IHDP). The European Union has launched a coastal core project (European Land-Ocean Interaction Studies

C. Identifying and Analyzing Watershed and Coastal Zone Problems
There are many kind of problem watershed and Coatal zone but The mostly problem in the watershed and coastal zone are soil erosion as the investigation of the drainage basin and coastal area revealed. Talus edges, rill erosion, sheet erosion, gully erosion, mass movements and badlands are widely spread throughout the River catchments and coastal area. Soil erosion processes are due to several physical and man-made factors here, including steep slopes, heavy rainfalls and intensive human activities (e.g., cultivation, Fishery pasture even in areas with steep slopes) resulting in high soil compaction. Soil conservation measures are not sufficient to reduce soil erosion processes. Soil erosion is a severe problem as it threatens livelihood security. Having identified and analyzed the problems of the watershed and coastal zone , clear and specific objectives have to be identified.
EROSION
Erosion is the removal of solids (sediment, soil, rock and other particles) in the natural environment. It usually occurs due to transport by wind, water, or ice; by down-slope creep of soil and other material under the force of gravity; or by living organisms, such as burrowing animals, in the case of bioregion .
Erosion is distinguished from weathering, which is the process of chemical or physical breakdown of the minerals in the rocks, although the two processes may occur concurrently.
Erosion is a noticeable intrinsic natural process but in many places it is increased by human land use. Poor land use practices include deforestation, overgrazing, unmanaged construction activity and road-building. Land that is used for the production of agricultural crops generally experiences a significant greater rate of erosion than that of land under natural vegetation. This is particularly true if tillage is used, which reduces vegetation cover on the surface of the soil and disturbs both soil structure and plant roots that would otherwise hold the soil in place. However, improved land use practices can limit erosion, using techniques such as terrace-building, conservation tillage practices, and tree planting.
Water erosion
One of example for water erosion is:

Sheet erosion is the detachment of soil particles by raindrop impact and their removal down slope by water flowing overland as a sheet instead of in definite channels or rills. The impact of the raindrop breaks apart the soil aggregate. Particles of clay, silt and sand fill the soil pores and reduce infiltration. After the surface pores are filled with sand, silt or clay, overland surface flow of water begins due to the lowering of infiltration rates. Once the rate of falling rain is faster than infiltration, runoff takes place. There are two stages of sheet erosion. The first is rain splash, in which soil particles are knocked into the air by raindrop impact. In the second stage, the loose particles are moved down slope by broad sheets of rapidly flowing water filled with sediment known as sheet floods. This stage of sheet erosion is generally produced by cloudbursts, sheet floods commonly travel short distances and last only for a short time.
Shoreline erosion
See also: Beach evolution


Erosion due to wave pounding at Venus Bay, South Australia.


Wave cut platform caused by erosion of cliffs by the sea, at Southern down in South Wales
Shoreline erosion, which occurs on both exposed and sheltered coasts, primarily occurs through the action of currents and waves but sea level (tidal) change can also play a role.
Hydraulic action takes place when air in a joint is suddenly compressed by a wave closing the entrance of the joint. This then cracks it. Wave pounding is when the sheer energy of the wave hitting the cliff or rock breaks pieces off. Abrasion or corrosion is caused by waves launching sea load at the cliff. It is the most effective and rapid form of shoreline erosion (not to be confused with corrosion). Corrosion is the dissolving of rock by carbonic acid in sea water. Limestone cliffs are particularly vulnerable to this kind of erosion. Attrition is where particles/sea load carried by the waves are worn down as they hit each other and the cliffs. This then makes the material easier to wash away. The material ends up as shingle and sand. Another significant source of erosion, particularly on carbonate coastlines, is the boring, scraping and grinding of organisms, a process termed bioregion.
Sediment is transported along the coast in the direction of the prevailing current (long shore drift). When the up current amount of sediment is less than the amount being carried away, erosion occurs. When the up current amount of sediment is greater, sand or gravel banks will tend to form. These banks may slowly migrate along the coast in the direction of the long shore drift, alternately protecting and exposing parts of the coastline. Where there is a bend in the coastline, quite often a build up of eroded material occurs forming a long narrow bank (a spit). Armored beaches and submerged offshore sandbanks may also protect parts of a coastline from erosion. Over the years, as the shoals gradually shift, the erosion may be redirected to attack different parts of the shore.

D. Relationship Beetwen Watershed and Coastal Zone
  Human activities on coastal watersheds provide the major sources of nutrients entering shallow coastal ecosystems. Nutrient loadings from watersheds are the most widespread factor that alters structure and function of receiving aquatic ecosystems.


To investigate this coupling of land to marine systems, we are studying a series of subwatersheds of Waquoit Bay that differ in degree of urbanization and hence are exposed to widely different nutrient loading rates. The subwatersheds differ in the number of septic tanks and the relative acreage of forests. In the area of our study, groundwater is the major mechanism that transports nutrients to coastal waters. Although there is some attenuation of nutrient concentrations within the aquifer or at the sediment-water interface, in urbanized areas there are significant increases in the nutrient content of groundwater arriving at the shore’s edge. The groundwater seeps or flows through the sediment-water boundary, and sufficient groundwater-borne nutrients (nitrogen in particular) traverse the sediment-water boundary to cause significant changes in the aquatic ecosystem. These loading-dependent alterations include increased nutrients in water, greater primary production by phytoplankton, and increased macroaglal biomass and growth (mediated by a suite of physiological responses to abundance of nutrients). The increased macroalgal biomass dominates the bay ecosystem through second- or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events. The increases in seaweeds have decreased the areas covered by eelgrass habitats. The change in habitat type, plus the increased frequency of anoxic events, change the composition of the benthic fauna. The data make evident the importance of bottom-up control in shallow coastal food webs. The coupling of land to sea by groundwater-borne nutrient transport is mediated by a complex series of steps; the cascade of processes make it unlikely to find a one-to-one relation between land use and conditions in the aquatic ecosystem. Study of the process and synthesis by appropriate models may provide a way to deal with the complexities of the coupling.

REFERENCES
K.J Gregory & D.E Walling, Drainage Basin Form and Process, Edward Arnold-Hill Street London. (1973)
Hardiatmo Christady Hary, Penaganan Tanah Longsor dan Erosi, Gadjah Mada University Press. Yogyakarta 2006
http://en.wikipedia.org/wiki/Erosion
Alongi D. M., 1998. Coastal ecosystem processes. 419 p. Boca Raton: CRC Press.
http://www.eoearth.org/article/Coastal_zone

http://www.geo.fu-berlin.de/fb/e-

learning/geolearning/en/watershed_management/planning_cycle/identify_problems/index.html
http://en.wikipedia.org/wiki/Drainage_basin
http://www.conservationinformation.com/?action=learningcenter_kyw_whatisawatershed