Slope Gradient & Drainage Efficiency

WSET notes that most vineyards are located on at least a gentle slope, and in some cases these can be extremely steep. Oregon State University Extension lists slope and aspect as the factors that determine a site's sunlight exposure patterns and duration, heat accumulation, and air and water drainage, and names air drainage, to avoid frost and freeze pockets, as a further topographic consideration. Sources report steepness in different units: Wines of Germany gives the Mosel's steep sites in degrees and the Bremmer Calmont as a percentage.

• WSET: the angle of the slope will impact how much sunshine the vines have access to, and a vineyard facing towards the equator will be warmer and sunnier than one facing away from it
• Wines of Germany: the sunshine on slopes is much more intense than on the plain, and south facing slopes benefit from a longer sunshine duration overall
• OSU Extension advises choosing a sloping area where possible, especially a south or southwest slope, because it generally has higher temperatures and is less likely to get frost
• AWRI: bare soil on slopes >5% predisposes a site to water erosion, especially if the soil's infiltration capacity is low

Bourgogne Wines names easier drainage as one advantage of hillside planting: on slopes, the water drains away more easily. The AWRI explains that waterlogging occurs when the root zone around the grapevine becomes saturated and the air between the soil particles is replaced by water, and its persistence is influenced by local topography and the drainage properties of the soil. Grapevine roots require oxygen for respiration, and a lack of oxygen over an extended period can result in root death. Oregon State University Extension adds that grape plants grow best in well-drained soils, and that heavy clay soils with poor drainage, or soils with an impervious subsoil clay pan, are not ideal.

• AWRI: hard, compacted soils and soils with shallow impermeable layers are particularly prone to waterlogging, and compaction is generally more of an issue in soils with a high clay content
• AWRI: when plants are growing actively, root tips begin to die within a few days of waterlogging, and the restricted root system that then develops limits the uptake of nutrients, particularly nitrogen, and water
• AWRI: in grapevines, the periods of active root growth, between flowering and veraison and after harvest, are very sensitive to waterlogging
• Air drainage: WSET explains that cool air tends to tumble down the hill and collect at the bottom, so vineyards on slopes are less affected by frost than those on the valley floor

According to the Mosel wine body's brochure, the rivers have carved their way deeply into the Rhenish Slate Mountains, and valleys with steep slopes were formed by the carving action of the Mosel and its tributaries. Wines of Germany describes the Calmont as a hill 290 metres high, rising between Bremm and Ediger-Eller, born 400 million years ago in the Devonian and made of slate rocks and weathered graywacke stones. From Zell onwards, the brochure notes, the slopes are in many cases so steep that the vines only find space in narrow terraces supported by retaining walls, and on the Calmont, walls made of slate rocks built horizontally across the slope save the soft clay slate soil from sliding down the slope.

• Douro: IVDP describes most of the Demarcated Region, particularly along the Douro River and its tributaries, as schistose with some granite around the edges
• Douro terraces: before planting, the schist was broken up by digging down deeply and forcing the vertically-layered rock to break up; this soil, found in the great majority of the land under vines, is designated aric anthrosoil (FAO/UNESCO 1988)
• Priorat: many vineyards are worked as costers (Catalan for steep slope), so steep that in some areas terraces have been built, and some terraces are so narrow that there is only space for two rows of vines
• AWRI: if the mid-rows are cultivated, terracing may be needed to control erosion, and erosion potential is much reduced when a cover crop is grown in the mid-rows

Bourgogne Wines states that planting the vines on slopes also ensures good ripening, and Vins Rhône says Côte-Rôtie wines owe their character to the area's very steep slopes. Wines of Germany writes that on the Calmont the steep slope causes an ideal angle of sun radiation, providing an optimal temperature for the growth of Riesling. In the Mosel, the steep slate slopes above the rivers store the sun's heat during the day and release it again at night, and the roots of the vines penetrate deep into the ground to seek water and minerals.

• Côte-Rôtie: the bedrock features a large number of fissures and fractures, allowing roots to find water and other nutrients (Vins Rhône)
• Douro: IVDP says the topsoil of clay mixed with broken schist penetrates between the vertical layers of rock, which protects it from water erosion, enables water to seep down to great depths to the roots of the vines, and holds the heat from the sun, helping the grapes to mature
• Mosel: the brochure notes that one major feature of slate is its ability to store heat, which is particularly advantageous on cool autumn nights
• Wines of Germany describes the Mosel's results as fine, fruity wines with an enormous depth of flavor and a relatively low alcohol content

Along the Mosel, Saar and Ruwer, around 5,000 winegrowers cultivate 8,287 hectares (2025), and Wines of Germany says nowhere in the world are there more steep vineyards. Côte-Rôtie, the northernmost appellation in the Rhône Valley, grows on slopes on the right bank of the Rhône between 180 and 325 m above sea level. DOQ Priorat's vines are distributed at altitudes from 100 metres above sea level up to 750 metres. The Douro Demarcated Region in Northeast Portugal spreads over a total area of approximately 250,000 hectares. In Bourgogne, the plots on slopes lie between 200 and 500 metres above sea level.

• Mosel: the Burg Cochem area on the lower Mosel is often called the terraced Mosel, as terracing is often the only possible way to grow vines on the radically steep slopes; the Bremmer Calmont is here
• Côte-Rôtie: almost all the vineyards are planted on metamorphic rock, with mica schist to the north, gneiss to the south and migmatite in the extreme south east
• Priorat: the DOQ is a member of CERVIM, an institute formed in 1987 under the leadership of the OIV for mountain viticulture, and it meets CERVIM's 'heroic' viticulture conditions, including little mechanization and small vineyards often organized on terraces
• Bourgogne: the hillside plots enjoy the best hours of sunshine, and this aspect also protects the vines from westerly winds which can bring humidity

The AWRI notes that under calm conditions the less dense warm air will rise and cold air settles close to the ground and especially into hollows, and that during radiation frosts, katabatic winds carry cold air downhill under the force of gravity. Oregon State University Extension adds that risk of frost injury varies a great deal among sites and even among locations on the same property. On the Calmont, grapes are harvested into baskets or buckets and carried down to the harvesting trolleys below, and since the 1990s a monorack train has eased some of this work. Wines of Germany reports that, because the work remains strenuous, only 13 of the Calmont's 22 hectares of vineyard space are still stocked with grapevines.

• AWRI: to minimise the impact of waterlogging, water should be encouraged to drain away, or be pumped from the vineyard, as soon as possible; a spoon drain dug in the centre of the traffic line helps promote surface drainage
• AWRI: waterlogging may continue even after surface water has dissipated, particularly in clay soils and soils with a shallow impermeable layer below the surface soil
• Mosel: on the steep inclines, growers tie each vine to its own eight-foot wooden stake and carry up the slate soil that has washed down with the winter rains (Wines of Germany)
• Priorat: some terraces are so narrow that the vineyard cannot be worked with farm machinery (DOQ Priorat)

Primary sources: https://www.wsetglobal.com/knowledge-centre/blog/2021/august/24/how-does-geography-affect-a-wine-s-style, https://www.winesofgermany.com/our-wine/viticulture/viticulture/178/soil-sites, https://www.winesofgermany.com/our-regions/growing-area/72/mosel, https://www.winesofgermany.com/our-regions/highlight-of-wine-culture/159/der-calmont, https://www.weinland-mosel.de/media/File/WeinbroschuereMosel2010GB.pdf, https://www.ivdp.pt/en/viticulture/region/characteristics-of-the-region/, https://www.doqpriorat.org/en/territory/, https://www.vins-rhone.com/en/cotes-du-rhone-cru-aoc-cote-rotie, https://www.bourgogne-wines.com/wine-and-terroir/our-natural-assets/climatology/an-ideal-climate-for-producing-great-wines,2483,9268.html, https://extension.oregonstate.edu/catalog/em-8973-establishing-vineyard-oregon-quick-start-resource-guide, https://extension.oregonstate.edu/sites/extd8/files/catalog/auto/EC1639.pdf, https://www.awri.com.au/files/attachment/managing-waterlogged-vineyards/, https://www.awri.com.au/wp-content/uploads/2017/10/Frost-fact-sheet.pdf, https://www.awri.com.au/wp-content/uploads/2018/06/vineyard-management-practices-to-improve-soil-health.pdf, https://www.doqpriorat.org/en/varietals/. Last verified 2026-09-28