Wadden Sea in the context of "Lower Elbe"

Jutland (/ˈdʒʌtlənd/), historically known as the Cimbrian Peninsula, is a peninsula in Northern Europe that forms the continental portion of Denmark and part of northern Germany (Schleswig-Holstein). It stretches from the Grenen spit in the north to the confluence of the Elbe and the Sude in the southeast. The historic southern border river of Jutland as a cultural-geographical region, which historically also included Southern Schleswig, is the Eider. The peninsula, on the other hand, also comprises areas south of the Eider: Holstein, the former duchy of Lauenburg, and most of Hamburg and Lübeck.

Jutland's geography is flat, with comparatively steep hills in the east and a barely noticeable ridge running through the center. West Jutland is characterised by open lands, heaths, plains, and peat bogs, while East Jutland is more fertile with lakes and lush forests. The southwestern coast is characterised by the Wadden Sea, a large, unique international coastal region stretching through Denmark, Germany, and the Netherlands. The peninsula's longest river is the Eider, which rises close to the Baltic but flows in the direction of the North Sea due to a moraine, while the Gudenå is the longest river of Denmark. In order for ships not having to go around the whole peninsula to reach the Baltic, the Kiel Canal – the world's busiest artificial waterway, crossing the peninsula in the south – was constructed.

Friesland (/ˈfriːzlənd/ FREEZ-lənd; Dutch: [ˈfrislɑnt] ; official West Frisian: Fryslân [ˈfrislɔ̃ːn] ), historically and traditionally known as Frisia (/ˈfriːʒə/), is a province of the Netherlands located in the country's northern part. It is situated west of Groningen, northwest of Drenthe and Overijssel, north of Flevoland, northeast of North Holland, and south of the Wadden Sea. As of January 2023, the province had a population of about 660,000, and a total area of 5,753 km (2,221 sq mi).

The land is mostly made up of grassland and has numerous lakes. The area of the province was once part of the ancient, larger region of Frisia, which gave the province its name. Friesland today is the home of the Netherlands's ethnic Frisian people. The official languages of Friesland are West Frisian and Dutch, and almost all West Frisian speakers are bilingual with Dutch.

A tidal creek or tidal channel is a narrow inlet or estuary that is affected by the ebb and flow of ocean tides. Thus, it has variable salinity and electrical conductivity over the tidal cycle, and flushes salts from inland soils. Tidal creeks are characterized by slow water velocity, resulting in buildup of fine, organic sediment in wetlands. Creeks may often be a dry to muddy channel with little or no flow at low tide, but with significant depth of water at high tide. Due to the temporal variability of water quality parameters within the tidally influenced zone, there are unique biota associated with tidal creeks which are often specialised to such zones. Nutrients and organic matter are delivered downstream to habitats normally lacking these, while the creeks also provide access to inland habitat for salt-water organisms.

Groningen (/ˈɡroʊnɪŋən/ GROH-ning-ən, UK also /ˈɡrɒnɪŋən/ GRON-ing-ən; Dutch: [ˈɣroːnɪŋə(n)] ; Gronings: Grunn; West Frisian: Grinslân [ˈɡrẽːslɔ̃ːn]) is the northeasternmost province of the Netherlands. It borders on Friesland to the west, Drenthe to the south, the German state of Lower Saxony to the east, and the Wadden Sea to the north. As of January 2023, Groningen had a population of about 596,000, and a total area of 2,955 km (1,141 sq mi).

Historically the area was at different times part of Frisia, the Frankish Empire, the Holy Roman Empire, and the Dutch Republic, the precursor state of the modern Netherlands. In the 14th century, the city of Groningen became a member of the Hanseatic League.

The Afsluitdijk (Dutch: [ˈɑfslœydɛik] ; West Frisian: Ofslútdyk [ˈɔfslyːdik]; "closure dyke") is a major dam and causeway in the Netherlands. It was constructed between 1927 and 1932 and runs from Den Oever in North Holland province to the village of Zurich in Friesland province, over a length of 32 kilometres (20 mi) and a width of 90 metres (300 ft), at an initial height above Amsterdam Ordnance Datum of between 6.7 metres (22 ft) along the section at Friesland, and 7.4 metres (24 ft) where it crosses the deep channel of the Vlieter. The height at the greater sea depths west of Friesland was required to be a minimum of 7 metres everywhere when originally constructed.

Increases to the height of the Afsluitdijk have been made several times since 1958 as part of regular maintenance since the deadly North Sea Flood of 1953. The section between the Stevinsluizen and Lorentzsluizen sluice complexes was raised to 7.8 metres. Major upgrade works commenced in 2019, with one of the design conditions being that only limited wave overtopping during the design storm condition be permitted. The design proposed by the successful contractor to meet this criterion will see a further increase in the height of the dam, by approximately 2 metres.

The Wadden Sea National Parks in Denmark, Germany and the Netherlands are located along the German Bight of the North Sea. In Germany and Denmark they also mark the area of the UNESCO World Heritage Site of the Wadden Sea. Divided from each other by administrative borders, they form a single ecological entity. The purpose of the national parks is the protection of the Wadden Sea ecoregion.

The North Frisian Islands (German: Nordfriesische Inseln, pronounced [ˈnɔʁtˌfʁiːzɪʃə ˈɪnzl̩n]; Öömrang and Fering North Frisian: Nuurdfresk Eilunen; Söl'ring North Frisian: Nuurđfriisk Ailönen; Danish: Nordfrisiske Øer) are the Frisian Islands off the coast of North Frisia.

The term covers both the North Frisian Islands in the narrow sense (in Schleswig-Holstein, Germany) and the Danish Wadden Sea Islands (in Denmark). However, culturally and linguistically, the Danish islands are usually not reckoned as being part of North Frisia, since they are not inhabited by native speakers of the North Frisian language. Occasionally, the remote island of Heligoland is also included in this group for reasons of administrative convenience, despite not being located in the Wadden Sea, since the island is home to its own unique dialect of Frisian.