Ditch in the context of "Freshwater molluscs"

The Antonine Wall (Latin: Vallum Antonini) was a turf fortification on stone foundations, built by the Romans across what is now the Central Belt of Scotland, between the Firth of Clyde and the Firth of Forth. Built some twenty years after Hadrian's Wall to the south, and intended to supersede it, while it was garrisoned it was the northernmost frontier barrier of the Roman Empire. It spanned approximately 63 kilometres (39 miles) and was about 3 metres (10 feet) high and 5 metres (16 feet) wide. Lidar scans have been carried out to establish the length of the wall and the Roman distance units used. Security was bolstered by a deep ditch on the northern side. It is thought that there was a wooden palisade on top of the turf. The barrier was the second of two "great walls" created by the Romans in Great Britain in the second century AD. Its ruins are less evident than those of the better-known and longer Hadrian's Wall to the south, primarily because the turf and wood wall has largely weathered away, unlike its stone-built southern predecessor.

Construction began in AD 142 at the order of Roman Emperor Antoninus Pius. Estimates of how long it took to complete vary widely, with six and twelve years most commonly proposed. Antoninus Pius never visited Britain, unlike his predecessor Hadrian. Pressure from the Caledonians probably led Antoninus to send the empire's troops farther north. The Antonine Wall was protected by 16 forts with small fortlets between them; troop movement was facilitated by a road linking all the sites known as the Military Way. The soldiers who built the wall commemorated the construction and their struggles with the Caledonians with decorative slabs, twenty of which survive. The wall was abandoned only eight years after completion, and the garrisons relocated rearward to Hadrian's Wall. Most of the wall and its associated fortifications have been destroyed over time, but some remains are visible. Many of these have come under the care of Historic Environment Scotland and the UNESCO World Heritage Committee.

A water supply network or water supply system is a system of engineered hydrologic and hydraulic components that provide water supply. A water supply system typically includes the following:

1. A drainage basin (see water purification – sources of drinking water)
2. A raw water collection point (above or below ground) where the water accumulates, such as a lake, a river, or groundwater from an underground aquifer. Raw water may be transferred using uncovered ground-level aqueducts, covered tunnels, or underground pipes to water purification facilities..
3. Water purification facilities. Treated water is transferred using water pipes (usually underground).
4. Water storage facilities such as reservoirs, water tanks, or water towers. Smaller water systems may store the water in cisterns or pressure vessels. Tall buildings may also need to store water locally in pressure vessels in order for the water to reach the upper floors.
5. Additional water pressurizing components such as pumping stations may need to be situated at the outlet of underground or aboveground reservoirs or cisterns (if gravity flow is impractical).
6. A pipe network for distribution of water to consumers (which may be private houses or industrial, commercial, or institution establishments) and other usage points (such as fire hydrants)
7. Connections to the sewers (underground pipes, or aboveground ditches in some developing countries) are generally found downstream of the water consumers, but the sewer system is considered to be a separate system, rather than part of the water supply system.

Water supply networks are often run by public utilities of the water industry.

Roman roads (Latin: viae Romanae [ˈwiae̯ roːˈmaːnae̯]; singular: via Romana [ˈwia roːˈmaːna]; meaning "Roman way") were physical infrastructure vital to the maintenance and development of the Roman state, built from about 300 BC through the expansion and consolidation of the Roman Republic and, later, the Roman Empire. They provided efficient means for the overland movement of armies, officials, civilians, inland carriage of official communications, and trade goods. Roman roads were of several kinds, ranging from small local roads to broad, long-distance highways built to connect cities, major towns and military bases. These major roads were often stone-paved and metaled, cambered for drainage, and were flanked by footpaths, bridleways and drainage ditches. They were laid along accurately surveyed courses, and some were cut through hills or conducted over rivers and ravines on bridgework. Sections could be supported over marshy ground on rafted or piled foundations.

At the peak of Rome's development, no fewer than 29 great military highways radiated from the capital, and the empire's 113 provinces were interconnected by 372 great roads. The whole comprised more than 400,000 kilometres (250,000 miles) of roads, of which over 80,500 kilometres (50,000 mi) were stone-paved. In Gaul alone, no less than 21,000 kilometres (13,000 mi) of roadways are said to have been improved, and in Britain at least 4,000 kilometres (2,500 mi). The courses (and sometimes the surfaces) of many Roman roads survived for millennia; some are overlaid by modern roads.

Freshwater molluscs are those members of the phylum Mollusca which live in freshwater habitats, both lotic (flowing water) such as rivers, streams, canals, springs, and cave streams (stygobite species) and lentic (still water) such as lakes, ponds (including temporary or vernal ponds), and ditches.

This article is about freshwater Mollusca in general; for information on one particular family of freshwater molluscs, please follow the appropriate links in the lists below.

Cross slope, cross fall or camber is a geometric feature of pavement surfaces: the transverse slope with respect to the horizon. It is a very important safety factor. Cross slope is provided to provide a drainage gradient so that water will run off the surface to a drainage system such as a street gutter or ditch. Inadequate cross slope will contribute to aquaplaning. On straight sections of normal two-lane roads, the pavement cross section is usually highest in the center and drains to both sides. In horizontal curves, the cross slope is banked into superelevation to reduce steering effort and lateral force required to go around the curve. All water drains to the inside of the curve. If the cross slope magnitude oscillates within 1–25 metres (3–82 ft), the body and payload of high (heavy) vehicles will experience high roll and lateral vibration.

Cross slope is usually expressed as a percentage:

A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom, the word can also be used for a longer artificially buried watercourse.

Culverts are commonly used both as cross-drains to relieve drainage of ditches at the roadside, and to pass water under a road at natural drainage and stream crossings. When they are found beneath roads, they are frequently empty. A culvert may also be a bridge-like structure designed to allow vehicle or pedestrian traffic to cross over the waterway while allowing adequate passage for the water. Dry culverts are used to channel a fire hose beneath a noise barrier for the ease of firefighting along a highway without the need or danger of placing hydrants along the roadway itself.

The Nanay River is a river in northern Peru. It is a tributary of the Amazon River, merging into this river at the city of Iquitos. The lower part of the Nanay flows to the north and west of the city, while the Itaya River flows to the south and east. Other nearby settlements on the Nanay River include the villages of Santo Tomás, Padre Cocha, and Santa Clara. During periods when the river is low, the many beaches along the Nanay are popular destinations. The Nanay belongs entirely to the lowlands, and is very crooked, has a slow current and divides into many canos and strings of lagoons which flood the flat, low areas of country on either side. It is simply the drainage ditch of districts which are extensively overflowed in the rainy season. Captain Archibald Butt USN, ascended it 195 mi (314 km), to near its source. A part of the Nanay River flows through the Allpahuayo-Mishana National Reserve.

The Nanay is a blackwater river and it has a high fish species richness, including several that are well known from the aquarium industry. Some of these, notably green discus, are the result of accidental introductions that happened in the 1970s.