Thusis is a municipality in the Viamala Region in the Swiss canton of Graubünden. On 1 January 2018 the former municipality of Mutten merged into the municipality of Thusis. Thusis is first mentioned in 1156 as Tosana. Thusis has an area, as of 2006, of 6.8 km2. Of this area, 18% is used for agricultural purposes, while 58.2% is forested. Of the rest of the land, 15.2% is settled and the remainder is non-productive. The municipality is the capital of the Thusis sub-district, of the Hinterrhein district, after 2017 it was part of the Viamala Region, it is the center of the Hinterrhein valley and is located at the confluence of the Hinterrhein and Nolla rivers. Thusis is at the end of the Viamala canyon, it consists of the village of Thusis and, since 1875, includes Übernolla. Thusis has a population of 9,269; as of 2008, 23.6% of the population was made up of foreign nationals. Over the last 10 years the population has grown at a rate of 0.7%. As of 2000, the gender distribution of the population was 50.4% male and 49.6% female.
The age distribution, as of 2000, in Thusis is. 142 people or 5.2% are 10 to 14, 141 people or 5.2% are 15 to 19. Of the adult population, 354 people or 13.0% of the population are between 20 and 29 years old. 460 people or 16.9% are 30 to 39, 402 people or 14.8% are 40 to 49, 333 people or 12.3% are 50 to 59. The senior population distribution is 255 people or 9.4% of the population are between 60 and 69 years old, 195 people or 7.2% are 70 to 79, there are 104 people or 3.8% who are 80 to 89, there are 27 people or 1.0% who are 90 to 99. In the 2007 federal election the most popular party was the SVP which received 31.4% of the vote. The next three most popular parties were the SPS, the FDP and the CVP. In Thusis about 63.5% of the population have completed either non-mandatory upper secondary education or additional higher education. Thusis has an unemployment rate of 1.65%. As of 2005, there were 15 people employed in the primary economic sector and about 5 businesses involved in this sector.
525 people are employed in the secondary sector and there are 36 businesses in this sector. 1,325 people are employed in the tertiary sector, with 190 businesses in this sector. From the 2000 census, 1,085 or 39.9% are Roman Catholic, while 1,096 or 40.3% belonged to the Swiss Reformed Church. Of the rest of the population, there are 134 individuals who belong to the Orthodox Church, there are 46 individuals who belong to another Christian church. There are less than 5 individuals who are Jewish, 96 who are Islamic. There are 64 individuals who belong to another church, 101 belong to no church, are agnostic or atheist, 95 individuals did not answer the question; the historical population is given in the following table: Most of the population speaks German, with Serbo-Croatian being second most common and Italian being third. Thusis has an average of 101.6 days of rain per year and on average receives 892 mm of precipitation. The wettest month is August. During this month there is precipitation for an average of 10.7 days.
The month with the most days of precipitation is June, with an average of 10.7, but with only 97 mm of precipitation. The driest month of the year is February with an average of 42 mm of precipitation over 10.7 days. Located a short distance to the southwest of Chur, Thusis is accessible using the A13 Autobahn. Rhätische Bahn operates services to Thusis. Anton Aberle a German–Swiss architect Luzius Rüedi a Swiss ice hockey player who won a bronze medal in the 1928 Winter Olympics Official website
The Aare or Aar is a tributary of the High Rhine and the longest river that both rises and ends within Switzerland. Its total length from its source to its junction with the Rhine comprises about 295 kilometres, during which distance it descends 1,565 m, draining an area of 17,779 km2 entirely within Switzerland, accounting for close to half the area of the country, including all of Central Switzerland. There are more than 40 hydroelectric plants along the course of the Aare River; the river's name dates to at least the La Tène period, it is attested as Nantaror "Aare valley" in the Berne zinc tablet. The name was Latinized as Arula/Arola/Araris; the Aare rises in the great Aargletschers of the Bernese Alps, in the canton of Bern and west of the Grimsel Pass. The Finsteraargletscher and Lauteraargletscher come together to form the Unteraargletscher, the main source of water for the Grimselsee; the Oberaargletscher feeds the Oberaarsee, which flows into the Grimselsee. The Aare leaves the Grimselsee just to the east to the Grimsel Hospiz, below the Grimsel Pass, flows northwest through the Haslital, forming on the way the magnificent Handegg Waterfall, 46 m, past Guttannen.
Right after Innertkirchen it is joined by the Gamderwasser. Less than 1 kilometre the river carves through a limestone ridge in the Aare Gorge, it is here that the Aare proves itself to be more than just a river, as it attracts thousands of tourists annually to the causeways through the gorge. A little past Meiringen, near Brienz, the river expands into Lake Brienz. Near the west end of the lake it indirectly receives its first important tributary, the Lütschine, by the Lake of Brienz, it runs across the swampy plain of the Bödeli between Interlaken and Unterseen before flowing into Lake Thun. Near the west end of Lake Thun, the river indirectly receives the waters of the Kander, which has just been joined by the Simme, by the Lake of Thun. Lake Thun marks the head of navigation. On flowing out of the lake it passes through Thun, flows through the city of Bern, passing beneath eighteen bridges and around the steeply-flanked peninsula on which the Old City of Berne is located; the river soon changes its northwesterly flow for a due westerly direction, but after receiving the Saane or La Sarine it turns north until it nears Aarberg.
There, in one of the major Swiss engineering feats of the 19th century, the Jura water correction, the river, which had rendered the countryside north of Bern a swampland through frequent flooding, was diverted by the Aare-Hagneck Canal into the Lac de Bienne. From the upper end of the lake, at Nidau, the river issues through the Nidau-Büren Canal called the Aare Canal, runs east to Büren; the lake absorbs huge amounts of eroded gravel and snowmelt that the river brings from the Alps, the former swamps have become fruitful plains: they are known as the "vegetable garden of Switzerland". From here the Aare flows northeast for a long distance, past the ambassador town Solothurn, Olten, near, the junction with the Suhre, Wildegg, where the Seetal Aabach falls in on the right. A short distance further, below Brugg it receives first the Reuss, its major tributary, shortly afterwards the Limmat, its second strongest tributary, it now turns to north, soon becomes itself a tributary of the Rhine, which it surpasses in volume when the two rivers unite downstream from Koblenz, opposite Waldshut in Germany.
The Rhine, in turn, empties into the North Sea after crossing into the Netherlands. Limmat Reppisch Sihl Alp Minster Lake Zurich Linthkanal Lake Walen Linth Löntsch Sernf Flätschbach Seez Reuss Lorze Kleine Emme Lake Lucerne Sarner Aa Engelberger Aa Muota Schächen Chärstelenbach Göschener Reuss Aabach Bünz Suhre Wyna Aabach Stegbach Dünnern Wigger Murg Rot Langete Ursenbach Rotbach Emme Lake of Bienne La Suze Zihlkanal Lake of Neuchatel La Broye Zihl/La Thielle L'Orbe Le Talent Saane/La Sarine Sense Gürbe Zulg Lake Thun Kander Simme Entschlige Lake Brienz Lütschine Gadmerwasser Lake Grimsel, 1,908 metres Lake Brienz, 564 metres Lake Thun, 558 metres Lake Wohlen, 481 metres Niederriedsee, 461 metres Lake Biel, 429 metres Klingnauer Stausee, 318 metres Anon. Atlas Routier et Touristique. Paris, France: Bordas-Tirade. Bridgwater, W.. "Aare". The Columbia-Viking Desk Encyclopedia. New York, NY: Columbia University Press. ISBN 978-0670230709. Cohen, Saul B. ed.. "Aare". The Columbia Gazetteer of the World.
New York, NY: Columbia University Press. ISBN 0-231-11040-5. Forbiger, Albert. Handbuch Der Alten Geographie. 3. Leipzig, Germany: Veriag von Gustav Mayer. Gresswell, R. Kay. Standard Encyclopedia of the World's Rivers and Lakes. New York, NY: G. P. Putnam's Sons. Hoib
Lake Constance is a lake on the Rhine at the northern foot of the Alps, consists of three bodies of water: the Obersee or Upper Lake Constance, the Untersee or Lower Lake Constance, a connecting stretch of the Rhine, called the Seerhein. These waterbodies lie within the Lake Constance Basin, part of the Alpine Foreland and through which the Rhine flows; the lake is situated in Germany and Austria. Its shorelines lie in the German states of Bavaria and Baden-Württemberg, the Austrian state of Vorarlberg, the Swiss cantons of Thurgau, St. Gallen, Schaffhausen; the Rhine flows into the lake from the south, with its original course forming the Austro-Swiss border, has its outflow on the "Lower Lake" where — except for Schaffhausen — it forms the German-Swiss border until the city of Basel. Lake Constance is the third largest freshwater lake in Central and Western Europe in terms of surface area, after Lake Geneva and Lake Balaton, it is 63 km long, at its widest point, nearly 14 km wide. It covers 536 km2, is 395 m above sea level.
The greatest depth is 252 metres, quite in the middle of the Upper Lake. Its volume is 48 km3; the lake has two parts: the main east section, called Obersee or "Upper Lake", covers about 473 square kilometres, to which its northwestern arm, the Überlinger See and the much smaller west section, summarizingly called Untersee or "Lower Lake", with an area of about 63 square kilometres. The connecting part between these two lake parts is the Seerhein. Geographically, it is sometimes not considered to be part of a river; the Lower Lake Constance is loosely divided into three sections around the Island of Reichenau: The two German parts, the Gnadensee north of the island and north of the peninsula of Mettnau, the Zeller See, south of Radolfzell and to the northwest of the Reichenau island, the Swiss Rheinsee – not to be mismatched with the Seerhein at its start! – to the south of the island and with its southwestern arm leading to its effluent in Stein am Rhein. The river water of the regulated Alpine Rhine flows into the lake in the southeast near Bregenz, Austria through the Upper Lake Constance hardly targeting the Überlinger See, into the Seerhein in the town of Konstanz through the Rheinsee without feeding both German parts of the Lower Lake, feeds the start of the High Rhine in Swiss town Stein am Rhein.
The lake itself is an important drinking water source for southwestern Germany. The culminating point of the lake's drainage basin is the Swiss peak Piz Russein of the Tödi massif of the Glarus Alps at 3,613 metres above sea level, it starts with the creek Aua da Russein. Car ferries link Romanshorn, Switzerland, to Friedrichshafen, Konstanz to Meersburg, all in Germany. Lake Constance is a zungenbecken lake. After the end of the last glacial period, about 10,000 years ago, the Obersee and Untersee still formed a single lake; the downward erosion of the High Rhine caused the lake level to sink and a sill, the Konstanzer Schwelle, to emerge. The Rhine, the Bregenzer Ach, the Dornbirner Ach carry sediments from the Alps to the lake, thus decreasing the depth and coastline extension of the lake in the southeast. In antiquity the two lakes still had different names. In the 19th century, there were five different local time zones around Lake Constance. Constance, belonging to the Grand Duchy of Baden, adhered to the Karlsruhe time, Friedrichshafen used the time of the Duchy of Württemberg, in Lindau, the Bavarian Munich time was observed, Bregenz used the Prague time, while the Swiss shore used the Berne time.
One would have needed to travel only 46 kilometers to visit five time zones. Given the amount of trade and traffic over Lake Constance, this led to serious confusion. Public clocks in harbors used three different clock faces, depending on the destinations offered by the boat companies. In 1892, all German territories used CET, the Austrian railways introduced CET in 1891, Switzerland followed in 1894; because traffic timetables had not been yet updated, CET became the sole valid time around and on Lake Constance in 1895. The Roman geographer, Pomponius Mela, was the first to mention the lake around 43 AD, calling it the Lacus Venetus and the Untersee Lacus Acronius, the Rhine passing through both. Around 75 AD, The naturalist Pliny the Elder called the entire Lake Constance, Lacus Raetiae Brigantinus after the main Roman town on the lake, Brigantium; this name is associated with the Celtic Brigantii who lived here, although it is not clear whether the place was named after the tribe or the inhabitants of the region were named after their main settlement.
Ammianus Marcellinus used the form Lacus Brigantiae. The current German name of Bodensee derives from the place name Bodman, which originally derived from the Old High German bodamon which meant "on the soils", indicating a place on level terrain by the lake; this place, situated at the west end of Lake Überlingen, had a more supraregional character for a certain period in the early Middle Ages as a Frankish imperial palace, Alamannian ducal seat and mint, why the name may have been transferred to the lake. From 833/
The Upper Rhine is the section of the Rhine in the Upper Rhine Plain between Basel in Switzerland and Bingen in Germany. The river is marked by Rhine-kilometres 170 to 529; the Upper Rhine is one of four sections of the river between the North Sea. The countries and states along the Upper Rhine are Switzerland and the German states of Baden-Württemberg, Rhineland-Palatinate and Hesse; the largest cities along the river are Basel, Strasbourg, Mannheim and Mainz. The Upper Rhine was straightened between 1817 and 1876 by Johann Gottfried Tulla and made navigable between 1928 and 1977; the Treaty of Versailles allows France to use the Upper Rhine for hydroelectricity in the Grand Canal d'Alsace. On the left bank are the French region of Alsace and the German state of Rhineland-Palatinate; the first few kilometres are in the Swiss city of Basel. Around 35 million years ago, a rift valley of about 300 kilometres long and 50 kilometres wide came into being between the present cities of Basel and Frankfurt.
This was due to tensile stresses in the Earth's crust and mantle, which resulted in lowering the earth's surface. The moat has been filled up again by sedimentation. On the edges we find mountain ridges, the so-called "rift flanks". On the eastern side, they are the Black Forest and Odenwald mountains, in the west the Vosges and Palatinate Forest. During the Tertiary, the High Rhine continued west from Basel and flowed via the Doubs and the Saône, into the Rhône; the rift diverted the Rhine into the newly formed Upper Rhine Valley. The Rhine knee at Basel marks the transition from the High Rhine to the Upper Rhine with a change of direction from West to North and a change of landscape from the small-chamber high-Rhine cuesta landscape to the wide rift zone of the Upper Rhine Rift Valley; the two largest tributaries come from the right: the Neckar in Mannheim, the Main across from Mainz. In the northwest corner of the Upper Rhine Valley, at Rhine-kilometre 529.1, near Bingen, where the Nahe flows into the Rhine, the Rhine flows into a gorge in the Rhenish Massif and thereby changes into the Middle Rhine.
In 1685, Louis XIV started a project to move the Upper Rhine, change its course and drain the floodplain, in order to gain land. By 1840, the river had been moved up to 1.5 kilometres to the east, taking territory away from Baden. Around 1790, large parts of the Rhine Valley were deforested, creating arable land and pasture to feed the population; the Upper Rhine was straightened between 1817 and 1876 by Johann Gottfried Tulla and changed from a sluggish meandering river with major and many smaller branches into a fast flowing stream flanked by embankments. The length of the Upper Rhine was reduced by 81 kilometres; some cut-off river arms and ox-bows remain. The Rhine between Basel and Iffezheim is entirely canalised. On a stretch of 180 kilometres, there are 10 dams, provided with hydropower locks. Between Basel and Breisach, the old river bed carries hardly any water. Only when there is a large supply of water the old river bed will receive more water than the canal. France gained the right to do this in the 1919 Treaty of Versailles.
The straightening and channeling reduced the water table by up to 16 metres and thus had a negative effect on flora and fauna. Gravel is missing from the river, due to the dams; this has caused erosion below the dam at Iffezheim. To counter this, 173,000 cubic metres per year of a mixture of sand and gravel with an average grain diameter of 20 millimetres has been dumped into the river, since 1978, using two motorized barges; the floodplains between Mainz and Bingen are important for nature conservation. In this section, the so-called Island Rhine, there are many nature reserves and bird sanctuaries; the Upper Rhine plays a key role in flood control on the Lower Rhine. As a result of the straightening of the Upper Rhine, floods from the Alps now reach the Middle Rhine much faster than in the past. Thus, the risk of such a peak coinciding with a flood peak of Neckar, Moselle or Main has increased. About 123 square kilometres of floodplain have been lost. Authorities in riparian states of France, Baden-Württemberg and Rhineland-Palatinate have launched the Integrated Rhine Programme, a framework for designating water retention areas.
To combat downstream flooding. A French-German treaty was concluded in 1982, in which the parties agreed to restore the retention capacity on the stretch below Iffezheim to the level it had before the area was developed; this means: For the stretch between Iffezheim and the mouth of the Neckar, attenuation of the apex of a 200-year flood of the Rhine to a discharge of 5,000 cubic metres per second at the Maxau gauge station, that is, a reduction from 5,700 cubic metres per second to 5,000 cubic metres per second. For the stretch below the mouth of the Neckar, attenuation of the apex of a 220-year flood to a discharge o
A river mouth is the part of a river where the river debouches into another river, a lake, a reservoir, a sea, or an ocean. The water from a river can enter the receiving body in a variety of different ways; the motion of a river is influenced by the relative density of the river compared to the receiving water, the rotation of the earth, any ambient motion in the receiving water, such as tides or seiches. If the river water has a higher density than the surface of the receiving water, the river water will plunge below the surface; the river water will either form an underflow or an interflow within the lake. However, if the river water is lighter than the receiving water, as is the case when fresh river water flows into the sea, the river water will float along the surface of the receiving water as an overflow. Alongside these advective transports, inflowing water will diffuse. At the mouth of a river, the change in flow condition can cause the river to drop any sediment it is carrying; this sediment deposition can generate a variety of landforms, such as deltas, sand bars and tie channels.
Many places in the United Kingdom take their names from their positions at the mouths of rivers, such as Plymouth and Great Yarmouth. Confluence River delta Estuary Liman
Geographic coordinate system
A geographic coordinate system is a coordinate system that enables every location on Earth to be specified by a set of numbers, letters or symbols. The coordinates are chosen such that one of the numbers represents a vertical position and two or three of the numbers represent a horizontal position. A common choice of coordinates is latitude and elevation. To specify a location on a plane requires a map projection; the invention of a geographic coordinate system is credited to Eratosthenes of Cyrene, who composed his now-lost Geography at the Library of Alexandria in the 3rd century BC. A century Hipparchus of Nicaea improved on this system by determining latitude from stellar measurements rather than solar altitude and determining longitude by timings of lunar eclipses, rather than dead reckoning. In the 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically-plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles, off the coast of western Africa around the Canary or Cape Verde Islands, measured north or south of the island of Rhodes off Asia Minor.
Ptolemy credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day. Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead. After their work was translated into Arabic in the 9th century, Al-Khwārizmī's Book of the Description of the Earth corrected Marinus' and Ptolemy's errors regarding the length of the Mediterranean Sea, causing medieval Arabic cartography to use a prime meridian around 10° east of Ptolemy's line. Mathematical cartography resumed in Europe following Maximus Planudes' recovery of Ptolemy's text a little before 1300. In 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, England as the zero-reference line; the Dominican Republic voted against the motion, while Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911.
In order to be unambiguous about the direction of "vertical" and the "horizontal" surface above which they are measuring, map-makers choose a reference ellipsoid with a given origin and orientation that best fits their need for the area they are mapping. They choose the most appropriate mapping of the spherical coordinate system onto that ellipsoid, called a terrestrial reference system or geodetic datum. Datums may be global, meaning that they represent the whole Earth, or they may be local, meaning that they represent an ellipsoid best-fit to only a portion of the Earth. Points on the Earth's surface move relative to each other due to continental plate motion and diurnal Earth tidal movement caused by the Moon and the Sun; this daily movement can be as much as a metre. Continental movement can be up to 10 m in a century. A weather system high-pressure area can cause a sinking of 5 mm. Scandinavia is rising by 1 cm a year as a result of the melting of the ice sheets of the last ice age, but neighbouring Scotland is rising by only 0.2 cm.
These changes are insignificant if a local datum is used, but are statistically significant if a global datum is used. Examples of global datums include World Geodetic System, the default datum used for the Global Positioning System, the International Terrestrial Reference Frame, used for estimating continental drift and crustal deformation; the distance to Earth's center can be used both for deep positions and for positions in space. Local datums chosen by a national cartographical organisation include the North American Datum, the European ED50, the British OSGB36. Given a location, the datum provides the latitude ϕ and longitude λ. In the United Kingdom there are three common latitude and height systems in use. WGS 84 differs at Greenwich from the one used on published maps OSGB36 by 112 m; the military system ED50, used by NATO, differs from about 120 m to 180 m. The latitude and longitude on a map made against a local datum may not be the same as one obtained from a GPS receiver. Coordinates from the mapping system can sometimes be changed into another datum using a simple translation.
For example, to convert from ETRF89 to the Irish Grid add 49 metres to the east, subtract 23.4 metres from the north. More one datum is changed into any other datum using a process called Helmert transformations; this involves converting the spherical coordinates into Cartesian coordinates and applying a seven parameter transformation, converting back. In popular GIS software, data projected in latitude/longitude is represented as a Geographic Coordinate System. For example, data in latitude/longitude if the datum is the North American Datum of 1983 is denoted by'GCS North American 1983'; the "latitude" of a point on Earth's surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth. Lines joining points of the same latitude trace circles on the surface of Earth called parallels, as they are parallel to the Equator and to each other; the North Pole is 90° N. The 0° parallel of latitude is designated the Equator, the fun
A floodplain or flood plain is an area of land adjacent to a stream or river which stretches from the banks of its channel to the base of the enclosing valley walls, which experiences flooding during periods of high discharge. The soils consist of levees and sands deposited during floods. Levees are the heaviest materials and they are deposited first. Floodplains are formed; when a river breaks its banks, it leaves behind layers of alluvium. These build up to create the floor of the plain. Floodplains contain unconsolidated sediments extending below the bed of the stream; these are accumulations of sand, loam, and/or clay, are important aquifers, the water drawn from them being pre-filtered compared to the water in the river. Geologically ancient floodplains are represented in the landscape by fluvial terraces; these are old floodplains that remain high above the present floodplain and indicate former courses of a stream. Sections of the Missouri River floodplain taken by the United States Geological Survey show a great variety of material of varying coarseness, the stream bed having been scoured at one place and filled at another by currents and floods of varying swiftness, so that sometimes the deposits are of coarse gravel, sometimes of fine sand or of fine silt.
It is probable that any section of such an alluvial plain would show deposits of a similar character. The floodplain during its formation is marked by meandering or anastomotic streams, oxbow lakes and bayous, marshes or stagnant pools, is completely covered with water; when the drainage system has ceased to act or is diverted for any reason, the floodplain may become a level area of great fertility, similar in appearance to the floor of an old lake. The floodplain differs, because it is not altogether flat, it has a gentle slope downstream, for a distance, from the side towards the center. The floodplain is the natural place for a river to dissipate its energy. Meanders form over the floodplain to slow down the flow of water and when the channel is at capacity the water spills over the floodplain where it is temporarily stored. In terms of flood management the upper part of the floodplain is crucial as this is where the flood water control starts. Artificial canalisation of the river here will have a major impact on wider flooding.
This is the basis of sustainable flood management. Floodplains can support rich ecosystems, both in quantity and diversity. Tugay forests form an ecosystem associated with floodplains in Central Asia, they are a category of riparian systems. A floodplain can contain 100 or 1,000 times as many species as a river. Wetting of the floodplain soil releases an immediate surge of nutrients: those left over from the last flood, those that result from the rapid decomposition of organic matter that has accumulated since then. Microscopic organisms thrive and larger species enter a rapid breeding cycle. Opportunistic feeders move in to take advantage; the production of nutrients falls away quickly. This makes floodplains valuable for agriculture. River flow rates are undergoing change following suit with climate change; this change is a threat to other floodplain forests. These forests have over time synced their seedling deposits after the spring peaks in flow to best take advantage of the nutrient rich soil generated by peak flow.
Many towns have been built on floodplains, where they are susceptible to flooding, for a number of reasons: access to fresh water. The worst of these, the worst natural disaster were the 1931 China floods, estimated to have killed millions; this had been preceded by the 1887 Yellow River flood, which killed around one million people, is the second-worst natural disaster in history. The extent of floodplain inundation depends in part on the flood magnitude, defined by the return period. In the United States the Federal Emergency Management Agency manages the National Flood Insurance Program; the NFIP offers insurance to properties located within a flood prone area, as defined by the Flood Insurance Rate Map, which depicts various flood risks for a community. The FIRM focuses on delineation of the 100-year flood inundation area known within the NFIP as the Special Flood Hazard Area. Where a detailed study of a waterway has been done, the 100-year floodplain will include the floodway, the critical portion of the floodplain which includes the stream channel and any adjacent areas that must be kept free of encroachments that might block flood flows or restrict storage of flood waters.
Another encountered term is the Special Flood Hazard Area, any area subject to inundation by the 100-year flood. A problem is that any alteration of the watershed upstream of the point in question can affect the ability of the watershed to handle water, thus affects the levels of the periodic floods. A large shopping center and parking lot, for example, may raise the levels of the 5-year, 100-year, other floods, but the maps are adjusted, are rendered