The West Hesse Depression[1][2] (German: Westhessische Senke) is part of the West Hesse Highlands and Lowlands region in the north of the German state of Hesse.
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The West Hesse Depression runs along the valleys of the Schwalm, Eder, Fulda, Esse and Diemel roughly from Alsfeld in the south to Bad Karlshafen in the north. It separates the East Hesse Highlands (major regional group 34 or D46), including the Knüll hills and Kaufungen Forest in the east, from the West Hesse Highlands (35 or D47), including the Kellerwald and Habichtswald in the west and is itself counted as part of the West Hesse Highlands, within which it is included as geographical unit 343. Its southern boundary is formed by the northern foothills of the Vogelsberg, which is part of the East Hesse Highlands region.[3]
The West Hesse Depression is part of the Mediterranean-Mjøsa Zone, a succession of troughs that run from the Rhone Valley through the Rhine Rift, the Wetterau and the Gießen Basin, below the Vogelsberg foothills to the Amöneburg Basin, and from there over the Neustadt Saddle in the West Hesse Depression and continuing along the Leine trough to the Oslo Rift valley.[4]
During the Mesozoic era, the deposits of the Zechstein Sea were overlaid with sand which then developed into Bunter sandstone. As a result of further uplifts and subsidence, Muschelkalk was deposited on top of the Bunter sandstone layer. In the subsequent Keuper geological stage the landscape rose and flooding alternated with the formation of swamps. In places the land also appears to have been reached by older phases of the Lias epoch.
The subsequent Alpine folding movements also had a lasting effect on the area. These caused the more rigid rock to shatter along fault lines resulting in sunken troughs or rifts and enabling volcanic outpourings to reach the surface. At the same time the surfaces of the surrounding ridges were eroded by weathering and rivers. So Keuper and Muschelkalk ridges emerged running through the area of Bunter sandstone in a northeast and northwest direction. As the Bunter weathered, layers of Palaeozoic rock were exposed again. As the Cainozoic era began, the Hesse Depression emerged, part of the great rift fault from Scandinavia to the Mediterranean Sea. This depression is surrounded by rolling hills on its eastern and western flanks. More recent rises and falls in the sea level led in the Tertiary period to flooding of the region and the deposition of sand. This covered the extensive forests that had grown up in the warm, moist climate, producing the lignite deposits evident today. Not until the recent period, the Quaternary, did the fertile loess soils of the West Hesse Depression appear.[5]
On the river plains of the Schwalm, Eder und Fulda the land of the West Hesse Depression is flat. Elsewhere the West Hesse Depression is a succession of ridges that rise to 300 m above NN (Weinkopf near Borken 298 m). The hill country is mainly covered by loess, in the north there are occasional rounded hills (Kuppen) of basalt and this is also where Mesozoic rocks are found at the surface; whereas tertiary sediments of gravel, sand and clay predominate in Hessengau. In the tertiary layers of the Borken Basin there are rich deposits of brown coal.[6]
The valleys of the following rivers are within the West Hesse Depression (rivers in brackets only drain the depression):
Ecologically important lakes within the depression are those created following the cessation of mining activity: the Borkener See and Singliser See.
| Natural regions of the West Hesse Depression | |||
|---|---|---|---|
| Number | Natural region | Area km² | Topographical map |
| 343.0 | Schwalm | ||
| 343.00 | Schwalm Bottom | 17,83 | TK25 Nr. 5121 |
| 343.01 | Wasenberg Terraces | 75,75 | TK25 Nr. 5121 |
| 343.02 | Alsfeld Hollow | 61,71 | TK25 Nr. 5221 |
| 343.1 | Landsburg Depression | ||
| 343.10 | Trockenerfurth Plain | 12,53 | TK25 Nr. 4921 |
| 343.11 | Landsburg Bottom | 36,20 | TK25 Nr. 5021 |
| 343.12 | Frielendorf Hills | 77,78 | TK25 Nr. 5021 |
| 343.13 | Borken Basin | 24,29 | TK25 Nr. 4921 |
| 343.2 | Hessengau | ||
| 343.20 | Homberg Bay | 42,02 | TK 25 Nr. 4922 |
| 343.21 | Wabern Plain | ||
| 343.210 | Schwalmaue | 22,43 | TK25 Nr. 4921 |
| 343.211 | Fritzlar Eder Corridor | 48,55 | TK25 Nr. 4821 |
| 343.22 | Großenenglise Plateau | 18,38 | TK25 Nr. 4921 |
| 343.23 | Fritzlar Börde | 96,37 | TK25 Nr. 4822 |
| 343.24 | Gudensberg Kuppen Ridge | 29,72 | TK25 Nr. 4822 |
| 343.3 | Kassel Basin | 250,62 | TK25 Nr. 4723 |
| 343.30 | Kassel-Fulda Aue | 17,49 | TK25 Nr. 4623 |
| 343.31 | Kassel Trough | 5,91 | TK25 Nr. 4622 |
| 343.4 | Hofgeismar Depression | 138,45 | TK25 Nr. 4422 |
| 343.5 | North Habichtswald Foreland | ||
| 343.50 | Westuffeln Depression | 31,77 | TK25 Nr. 4522 |
| 343.51 | Langenberg and Staufenberg Plateau | 29,52 | TK25 Nr. 4522 |
Taken from the Hesse Environmental Atlas (Umweltatlas Hessen):[7]
The natural region of the West Hesse Depression is characterised by numerous smaller depressions and plains.
From its southern end, the West Hesse Depression runs in a northwesterly direction through the Schwalm (region) (343.0) which surrounds the upper and middle course of the river of the same name, beginning with the Alsfeld Hollow (Alsfelder Mulde) followed by the Wasenberg Terraces and the Schwalm Bottom (Schwalmgrund).
Continuing in a northeasterly direction around the middle reaches of the Schwalm is the Landsburg Depression (343.1) with its sub-units the Landsburg Bottom, Frielendorf Hills, Trockenerfurth Plain and the Borken Basin.
The transition into the Hessengau region (343.2) with the confluence of the Schwalm and the Eder continues northeast via the regional sub-units of the Homberg Bay, Wabern Plain (Schwalmaue and Fritzlar Eder Corridor), Großenenglis Plateau, Fritzlar Börde and the Gudensberg Kuppen Ridge into the Kassel Basin.
In the Kassel Basin (343.3) by the lower course of the Fulda with its sub-units the Kassel Fulda Aue and Kassel Trough the West Hesse Depressino swings northwest again and leaves the catchment area of the Fulda, to enter that of the Diemel.
To the northwest it runs along the Nebelbeeke and the Warme which drains into the Diemel, and into the North Habichtswald Foreland with its sub-units of the Westuffeln Depression and the Langenberg and Staufenberg Plateau.
Northeast of the Kassel Basin are the Hofgeismar Depression, which follows the Esse (Diemel) and finally the lower course of the Diemel until just before its confluence with the Weser. This natural region has an area of 138.45 square kilometres and is the second largest within the West Hesse Depression.
The origin of the name "West Hesse" can only be understood and derived from the neighbouring natural region of the East Hesse Highlands. The catchment area draining northwards into the River Weser can be referred to as a North Hesse Depression.[7]
In the West Hesse Depression are:[6]
Especially important avifauna regions are found near Borken (Hessen), where the Tagebau Gombeth is a breeding area of national significance. Other areas of national importance are:
Of regional significance is the Ems river, a breeding and wintering area.
The Borkener See nature reserve (332 ha) is also a Special Area of Conservation.[6]