The Broads are an extensive collection of shallow man-made lakes in the Norfolk and Suffolk counties of England found along the rivers Ant, Thurne, Bure, Yare, Chet, and Waveney.
The Broads were originally started in the Middle Ages as monks cut and dried peat to sell as heating and cooking fuel to Norwich and Great Yarmouth1. Norfolk was home to some deep peat beds, many of them more than 3 meters deep, which produced higher quality peat; harvesting this 'brushwood peat' resulted in deep peat pits, although more shallow peat beds, 1-2 meters in depth, were also common and were also extensively harvested. Once these earthworks filled in with water, the shallow harvest beds quickly became fen land, shallow wetlands covered in reed and sedge. The deeper pits became the Broads.
Most navigable broads are 'side-valley' broads, not along the river proper, but widening of tributaries entering the main rivers. Because peat was harvested in giant open-top trenches, old baulks are still sometimes apparent as narrow peninsulas or small islands. In the past submerged ridges of this sort posed a danger to unwary boaters, but dredging has long since cleared most of these obstacles.2
While the best known broads are along, or at least connected to, a river, there are also 'by-passed' broads, which are not connected to the rivers. These broads may stand some way away from the rivers, but they are just as likely to stand along the river separated by a narrow baulks of unharvested peat. Most of these are currently protected wetlands, although in the past attempts had been made to connect them to extend the navigable waterways, and may still be navigable by small craft.
All of this is a comparatively recent rediscovery; the naturalist Samuel Woodward suggested that the broads might be man made in 1834, but it wasn't until 1960 that ecologist Joyce Lambert published a definitive review of the evidence, including her own original work, that finally settled the matter. Once people know what to look for (peat baulks, artificial cuts, and differences in soil types, and historical evidence from monastery records), it became clear that Lambert was correct.
It has been estimated that 900 million cubic feet of peat were excavated to create the broads, although any estimate is difficult -- in part because the last few centuries have seen many attempts to drain fen land, and historical documents list broads that no longer exist, having either been drained completely or becoming silted in to become reed and sedge beds.
The reed and sedge beds, generally termed 'fens', are also an important part of England's historical economy, and are now ecologically important. Norfolk reed and sedge from the Broads was primarily used for thatching and weaving, and to some extent still is today. If fens are not cut every 3-5 years, the dead plant matter builds up to the point that the ground rises above water level, and the fens turn to carr woodland (primarily willow, alder, and osier). Because of this, those reed beds that still exist are regularly harvested by the government whether the thatch is needed or not.
Because the Broads are home to many of the United Kingdom's rarest species3, the Broads Authority manages not only the economic needs of the Broads, but also the ecological conservation. The Broads are considered a wildlife preserve, but because they include many private lands they have not been made into a public park. The Broads Authority works to preserve the Broads (including through dredging) and the fens (including through controlled commercial harvesting), protecting them not only from human development but also preventing natural processes from reclaiming the ecosystem.
While I am primarily interested in the ecology and history of the Broads, the term most often refers to the geographical area, which includes a number of important towns and cities and which is known for good sailing, bird watching, and generally being an all-around good spot to commune with nature. The Broads stretch from Norwich inland, out to Great Yarmouth and Lowestoft on the coast, and with extensive penetration up north to Ludham, Wroxham, and Stalham, and out to Bungay in the south-west.
1. While the monks did much of the work, smaller scale peat harvesting continued into the early 1900s.
2. It is interesting to note that parish boundaries sometimes followed these ridges, and thus many boundaries can be found in mid-stream, and may change directions for no apparent reason when passing through a broad. It has also been suggested, however, that the causality runs the other way -- communal peat cuttings may have been undertaken at parish boundaries where the communities could work together. Of course, it also helps that parish boundaries tend to occur at natural waterways, and peat is found in lowlands that were once marsh -- both of which occur in the lowest lying areas.
3. The term "rarest species" is used for a reason; many of these species occur nowhere else in the UK, but do occur elsewhere in Europe; while some species may be referred to as endangered -- or in some cases, recently extinct -- this refers to their existence in the UK specifically.