The River Effra is alive and well, and living in Dulwich!
Yes - you did read aright! You may not be directly aware of the river above ground in much of Lambeth, but after rain you can often hear it under your feet, and its effects on the landscape are to be seen in much of South London, if you know what to look for and where to look. Although the former course of this small but well-documented southern tributary of the Thames is well-known from its main sources in Upper Norwood to its outfall near Vauxhall, it is sometimes referred to as 'Lambeth's lost river' since it has been culverted under the streets of London for over 150 years. The lower part was navigable in Elizabethan times (the Queen herself used it to visit some of her court favourites, and once picknicked under the tree that gave its name to Honor Oak), but alas, no more! Recently the Mayor of London announced that stretches of the Effra, along with other hidden London rivers, are to see the light of day once again. However, as I hope to demonstrate, some parts of the Effra's upper reaches can already be seen above ground in that part of its basin that focuses on Dulwich, and many of its original sources were not in Lambeth at all, but in the neighbouring Boroughs of Croydon and Southwark, and even in more distant Lewisham. There has been some controversy over the full extent of the Effra's drainage basin, the main course of the river and its tributaries, and its significance in South London, all of which I shall examine here. As a geogapher I hope to illustrate ways in which the River Effra helped to shape the patterns of land use, transport and settlement in South London, and to give Dulwich in particular its distinctive character.
a) Location and outline of the Effra Basin:
Map 1 : Reconstruction of the former drainage basin of the River Effra.
The Effra drainage basin is located in the central area of inner south London, focusing on the River Thames at Vauxhall. It is a rough rectangle, its long axis aligned from SSE to NNW, narrowing slightly in that direction. Its southern and south-eastern watershed (marked in brown above) is the 100m high, steep, narrow ridge that extends from Upper Norwood (near the borders of Lambeth and Croydon), along Sydenham Hill (in Southwark) to Westwood Park (just in Lewisham). There is just one col cutting across the ridge - carrying the South Circular Road at Horniman's, Forest Hill (picture 1). Few other roads cross the ridge directly, and railways skirt round it or tunnel through. Drainage south and east of this main watershed is to the Pool River, which joins the Ravensbourne in Catford, and reaches the Thames via Deptford Creek. Drainage to north and east is via the Peck and Neckinger to Surrey Docks.
1. The Sydenham Hill watershed. Hornimans is on the left; 2. The easternmost source of the Effra, along all rain here drains to the Effra via Dulwich (off to the right). Hornimans' Railway Nature Trail.
The western watershed is a northward-projecting spur from the Norwood Ridge that separates the Effra from its much larger neighbour, the Wandle; the latter reaches the Thames at Wandsworth. The north-eastern watershed consists of lower and less regular slopes that separate the Effra from the former River Peck and the Earl's Sluice that fed Surrey Docks and the Surrey Canal. There is a secondary interfluve between Crystal Palace and Herne Hill that separates the Sydenham and Dulwich part of the Effra basin from Norwood and Brixton. The Effra is a small basin - only about 20 sq km. The maximum stream length (between Westwood Park and Vauxhall) was just over 9 km; the altitude range within the basin is about 111 metres or 360 feet. The highest point (at Upper Norwood) is also the southernmost, but there was a continuous line of springs at between 80 and 100 m OD along the imposing 5 km ridge that was Surrey's 'Great North Wood'. The Effra headwaters they fed followed different paths to the main confluence at Brixton, viz: (i) from Streatham Hill, Beulah Spa and Norwood Park directly via West Norwood, (ii) from Gypsy Hill and Crystal Palace via West Dulwich and Herne Hill, (iii) from Rockhills and Dulwich Wood via Belair Park and Herne Hill, (iv) from Peckarmans Wood and Sydenham Hill via Dulwich Common and Herne Hill, (v) from Eliot Bank, Hornimans Park, and Westwood Park via Lordship Lane, Dulwich and Herne Hill. There were also springs at lower altitude in East Dulwich (eg Dawson's Hill), North Dulwich (eg Sunray Gardens), Tulse Hill, and at the base of the Thames river terraces further downstream (eg Stockwell), as well as indeterminate drainage in the floodplain around Vauxhall and Kennington. b) Rocks, Soils and Land Use:
Geological Background: Most of our area is underlain by young sedimentary rocks, deposited about 8 m years ago in an ancient sea that invaded a deepening down-fold of the Chalk rocks that occupied most of what is now southern Britain and Northern France. The sediments were initially coastal sands and gravels, but as the sea deepened, great thicknesses of offshore muds were laid down - these became the London Clay. Further short marine transgressions deposited thin layers of younger, less consolidated sands and gravels on top, before the whole assemblage was uplifted, tilted, exposed to the elements, and weathered. This produced the funnel-shaped London Basin we see today: with Chalk at the base (exposed south of our area in the North Downs), then Bagshot Sands (found mainly as sandy heathland south and west of London), next the London Clay which dominates most of the region, and finally the Woolwich and Reading Beds which locally provided a protective pebbly cap on top. The fore-runner of the modern Thames initially drained this basin east-north-east across plains that are now occupied by the North Sea, but the development of the drainage pattern was interrupted in a big way by the Pleistocene Ice Age(s) from about 2 million years ago. Ice sheets spread into the northern part of the region and diverted the proto-Thames trunk stream southwards to approximately its present west-east line. Powerful meltwater streams gouged out the existing main and tributary valleys and spread material from the ice ( drift) over tundra-like frozen ground, well beyond the ice front. When the ice finally retreated 10 000 years ago the topography, soil, drainage pattern, and even the climate, were very different from that either before or since. This was a new landscape and environment to which the newly forming Effra and its neighbours had to adapt - a process that is still not complete.
Soils, slopes and landforms: London Clay is the bedrock underlying nearly all of our basin. It is a stiff bluish-grey clay when undisturbed underground, but it weathers very quickly upon exposure to a pale yellowish brown colour, which becomes dark brown where soils have formed on it. It is composed of very fine-grained clay particles with the tiniest pore spaces in between. These quickly become filled with rain water, which can only permeate and move through the soil very slowly by capillary action, and therefore the soil is normally heavy and cloying because of its high water content (as local gardeners will testify), and highly impermeable. It will expand readily and heave upward if the interstitial water freezes. However, when it dries out in summer it shrinks, cracks open up at the surface, and the soil particles lose their physical and chemical bonds: the soil can then become very friable and susceptible to erosion by running water. In hollows and at the foot of slopes water collects quickly, can't drain away, the ground becomes waterlogged and puddles form, as happens frequently below Dulwich and Sydenham Woods, acting like a giant sponge (picture 4). Regular cycles of wetting and drying, freezing and thawing, expansion and contraction, have the effect of causing the soil to creep rapidly and steadily downhill. In extreme circumstances a whole soil mass will slump or slip, producing irregular and unstable slope profiles and potential engineering and structural problems, as the early railway builders and many local residents (including St Stephen's Church, South Dulwich), have discovered to their cost.
Because it is soft, and weathers and erodes easily, London Clay generally forms areas of low relief, but the southern rim of our basin rises to over a hundred metres above sea level in less than 10 kms, with locally very steep gradients. This is partly because of the 3 metre gravel capping that covered and protected the clay here, particularly at Crystal Palace and Upper Norwood. The gravels, though only partially consolidated, were more resistant to physical and chemical weathering than the clay beneath them, and they readily absorbed rainwater, rather than shedding it as runoff and initiating erosion. However, when the rainwater percolating through the gravel reached the impermeable clay beneath it ran along the junction until it reached the ground surface below the summit ridge to form the line of Effra springs (picture 12). The level in the rocks below which they are saturated with percolating water is called the water table, and its depth below ground level tends to fluctuate according to how much rain there has been. The water table here, as in most of Britain, has lowered considerably in recent years, so the former springs are now dry. However, water still collects at the surface after rain, and there are semi-permanent springs lower down. It is likely this lowering of the water table will continue in the future under the influence of global warming. Water issuing from springs tends to sap or undercut the slope above, causing it to steepen and slowly retreat, evidence for which can clearly be seen in Dulwich Woods (picture 5b). Furthermore, these slopes face north and receive little sun, particularly in winter, and therefore they are also very susceptible to the freeze-thaw action described above; this reinforces and accelerates the steepening effect. In the lower reaches of the Effra basin the London Clay is locally covered with a veneer of superficial sands and gravels deposited in the valleys by the proto-Thames and its tributaries at the end of the Ice Age. These deposits were then eroded and cut back to form river terraces raised above the floodplain, some of which make up the lower interfluves of Lambeth and Southwark. These also fed springs, formed islands in the marshes, and provided firm dry sites for building houses, roads, and railways, hence facilitating the explosive growth of South London in the 18th and 19th centuries.
3 Looking down the dry valley of the Effra on Dulwich and Sydenham Hill Golf Course. 4 Overland flow (runoff) on the gentler slopes Note the terrace in the foreground, and the steepening towards Dulwich Common. of Dulwich Common, draining from Sydenham Hill. .
Land use, vegetation and environment: There are significant contrasts between the Dulwich and Lambeth parts of the Effra Basin in the way the land is used, most notably in the ratio of built up area to open land. In the basin as a whole, approximately three-quarters of the land is classed as built-up (consisting of residential, industrial, commercial and public buildings - with their curtelage - and the transport infrastructure that serves them), whilst the remaining quarter is classed as open land (which here is mainly parks, playing fields, and cemeteries). This built up/open land ratio is not as high as might be expected in the Inner South London Boroughs of Lambeth and Southwark (which are generally perceived as being particularly overcrowded), but the ratio does increase substantially from south to north (ie from Norwood to Kennington and beyond), which is what one would expect. What is surprising, though, is that this built up/open land ratio decreases very sharply (to less than parity) in Dulwich. There can be few areas of comparable size within five miles of the centre of any metropolis that can claim to have less than half of the land built over, as Dulwich can. Moreover, this inner city area includes a significant swathe of natural woodland, three Nature Reserves, and an 18-hole Golf Course, in addition o parks, allotments and sports grounds (pictures 3 and 4). It is not that the land is difficult to build on, or that it is not in demand - far from it: Dulwich is one of the most sought after residential addresses outside London's West End. So how has this anomalous situation come about, and what is its significance?
The woodland is the surviving part of the Great North Wood of Surrey (to distinguish it from the Forest of the Weald further south). It has been considerably modified over many centuries by human activity. Clothing the steep-sided Norwood and Sydenham Heights, it was a natural boundary between the growing London metropolis and its rural hinterland, as well as an important resource. The steep slopes, wet soils, and dense vegetation made it a place of refuge rather than permanent settlement until recently, but it has been coppiced since medieval times, for building, firewood, and making charcoal. Only in the 19th century, as transport improved and London's environment deteriorated, did wealthier citizens move to the higher parts of Norwood, Sydenham, and Forest Hill to take advantage of the fresh hill air, clean spring water, and sweeping vistas of the Effra watershed. These large houses and gardens were inevitably expensive to maintain, and most were either converted into flats and nursing homes, or replaced by smaller, higher density properties. While the original forest was dominated by native oak, hornbeam and yew, the woodland we see now has a much greater variety that includes introduced species like sycamore and horse chestnut, colonisers such as holly and birch, and escaped garden shrubs and trees. In response to public pressure, much of the remaining woodland is now protected and managed by ecological groups, local authorities, and private landowners (such as Dulwich Estates). On the lower slopes of the ridge, Dulwich and Sydenham Woods give way to allotments, the Golf Course, and playing fields. This was the original Dulwich Common - largely unimproved grassland used for the common grazing of livestock, since the land was wet and subject to downslope drainage of cold air in winter, and relatively inaccessible because it was marginal to the ancient monastic and manorial landowners, and the Parishes which took over their social and administrative functions. Further north still, around Dulwich Village, the confluence of the growing Effra headwaters produced the lush water meadows used mainly for dairying and livestock fattening as London's demand for food grew. Accessibility was better here, but unlike neighbouring Camberwell and Peckham the wetter soils were not suitable for crop growing or for market gardening. This land was the main part of the Manor of Dulwich that Edward Alleyn acquired, and where he built his College of God's Gift. As a reult of careful management and deliberate policy it is still occupied mainly by the Old College, its modern successor (later rebuilt on Dulwich Common), Belair Park and Dulwich Park (where Dulwich Court Farm used to be), and more recently by several sports' clubs. Residential development has been confined almost entirely to the margins of the Dulwich basin where are located still the only through roads and railways - along Lordship Lane in the east, Upper Sydenham and Crystal Palace in the south, Herne Hill and Denmark Hill in the north, and West Dulwich and 'the Norwoods' on the west. This house-building began in the 18th century as upper middle class ribbon development along coaching routes such as the Brighton and Portsmouth roads, then from the mid-19th century as nodes around railway stations like Herne Hill and West Norwood, before spreading out and joining up in the later 19th and 20th centuries as omnibuses, trams, bicycles and motor cars became increasingly widespread. Working class housing was packed into less salubrious plots within walking distance of factories and other places of low-paid employment, eg backing onto railway lines (such as those at Loughborough Junction), or near gas works and other public utilities, as at Nine Elms (Vauxhall). Commerce and public services such as shops, schools, churches etc broadly followed the residential development, but it is notable that there were no markets in south Lambeth or Dulwich. Industry has always been constrained by the need for access to cheap land, labour and materials - firstly via navigable water, then railways, and more recently trunk roads. These were only to be found in the Thamesside part of the Effra basin from Waterloo to Nine Elms. Norwood and Brixton may have their share of shops and public services, and even some offices and light industry, but it is notable that Dulwich is characterised (some would say dominated!) by no less than six large schools (four of them well-known independent schools), whilst commerce and industry are almost completely absent. It is well-known for its Picture Gallery and cultural societies, and literally on its borders are Horniman's Museum and the site of the Crystal Palace - a stimulating cultural environment indeed. While it would seem that these defining characteristics of Dulwich can ultimately be traced back to the vision of Edward Alleyn and to his successors, the Estates Governors, as well as to the influence of a number of influential landowners and residents, it is also undoubtedly true that the environment and physical features of the Effra Basin had a major part to play.
c) Following the Effra downstream:
Diagram 1: Reconstructed Valley Profile from Sydenham Hill to Vauxhall, via Dulwich and Brixton:
The profile above has been reconstructed with the aid of Ordnance Survey map data, supple-mented and verified by study of the slopes on the ground. It broadly shows the typical concave -upward long profile of most rivers in temperate latitudes, but it is not completely smooth: there is local steepening on the Golf Course (picture 3), in Dulwich Park, and beyond Herne Hill (picture 9), with flatter profiles on Dulwich Common (picture 4) and approaching Herne Hill (picture 8). The steeper gradients occur where tributaries join, increasing the stream's erosive action; the flatter sections are surviving fragments of earlier flood plain where deposition took place. The long profile is steeper than would be expected in a short, lowland stream in Britain, particularly so in its source region, and it has a very short flat flood plain section close to its mouth relative to its overall length. Nor is the drainage basin symmetrical in shape (the longer tributaries are from the east, not the south or west), and the inferred stream pattern is of high density, especially in its upper and middle reaches. All this suggests a relatively young stream that has not had time to adjust fully to present day topographic and climatic conditions, and one where significant changes in its environment and discharge have occurred over the years. Such youthful or disrupted rivers are more volatile in behaviour, and flood more readily than their fully graded counterparts, one of the reasons the Effra was culverted downstream. These characteristics can be explained by the underlying geology (mainly London Clay), by its climatic and morphological history (initiated at the end of the Ice Age and subject to fluctuating discharge and a high water table ever since), by its location near the mouth of the River Thames (which is sinking, is tidal, and used to be subject to flooding and changes of course), and the growth of London (which constrained then culverted the channel, and caused increased runoff). 
5a The artificial leat collects spring water and runoff from the steep 5b The Ambrook River (Effra headwater in Peckarmans Wood). slope belowthe Sydenham Hill watershed, to reduce erosion of the path. Note the highly compacted soil, and steep rounded slopes.
6 The view from Dulwich & Sydenham Hill Golf Club, across the Dulwich basin to the West Norwood watershed (on the skyline). Dulwich College is in the middle ground. The Herne Hill gap is the lower ground behind and to the right, with West London visible through it.
The stream course we shall concentrate on is neither the main Norwood stream nor the longest Forest Hill branch, but an intermediate one that is more typical of the whole, and easier to identify and follow. It begins at former springs which can be accessed from a gate near the junction of Crescent Wood Road and Sydenham Hill, SE26. They are in the central and highest part of the spring line that extended in an arc for about 8 kms along the ridge of hills between Streatham Common and Nunhead. Rising at about 105 metres OD, rills and gulleys drain steeply down in a north-easterly direction (picture 5) as the Ambrook river, through small ponds in Sydenham Woods to the edge of the Dulwich and Sydenham Hill Golf Course at about 60 m OD. Here there is a near level terrace on which the allotments, Clubhouse and South London Scout Centre are located. The stream now follows an obvious valley (now dry - picture 3) which turns north towards The Grove Tavern on Dulwich Common (the site of Dulwich Wells, which for a short time in the 18th century rivalled the better known Sydenham Wells and Beulah Spa). Our stream was then joined by other headwaters flowing from East Dulwich and Forest Hill (see pictures 1 and 2a above), and flowed north-west across what were once the water meadows of Dulwich Court Farm, now Dulwich Park. There is no channel to follow here, only an irregular line of old trees winding towards the Park Lake. The river drains the lake over a metre high waterfall and turns north-west towards Old Dulwich College in a prominent 2 metre wide channel (see picture 7). By the Old College Gate it used to be joined by a ditch that brought more tributaries from Sydenham Hill via Dulwich Mill Pond (this was later covered over to produce College Road's wide grass verge, but a short stretch outside Bell House still carries occasional storm water).
7a. The Dulwich & Sydenham Hill branch of the Effra in Dulwich Park. 7b. The West Dulwich branch at Belair.
From the Old College downstream the river flows entirely underground, although it is still possible to trace its route by following surface contours and the lie of the land. It continued across former marshy meadows (now playing fields) in West Dulwich to be joined by more Effra headwaters from Crystal Palace (some of that water is still visible just to the south in Belair Park - picture 7b). The water meadows around Dulwich Village were the eponymous "Dilwyhs" (fields where the dill flower grew). They sit in the bottom of a north-tilted saucer whose rim is the watershed of the Dulwich part of the Effra drainage basin (picture 6). The only way for the water to exit the Dulwich basin was via a narrow gap in the rim at Herne Hill resulting from a deep-seated fault in the rocks. These combined Effra headwaters approached Herne Hill via present-day Winterbrook Road, turned west through the gap to Brockwell Park, to be joined by further tributaries from West Norwood (pictures 8 & 9). It in turn joined the main Effra River flowing from Upper Norwood and Streatham Hill via Brixton Water Lane (sic) and Effra Road, continuing north to Kennington and finally west to Vauxhall. (The last section of the river is shown on my profile as a dotted line because the position of its confluence with the Thames was variable until it was finally stabilised by the Metropolitan Board of Works in the 19th century.)
8. The Herne Hill gap from Brockwell Park. The Dulwich branch of the Effra came in from the right (approximately at the railway bridge), was joined by tributaries from West Dulwich and Norwood, then continued left along the line of Dulwich Road (picture 9). Note the railway was built up on embankments to cross the marshy ground here.
9. Looking WNW from Herne Hill. The Effra followed this line towards the main Effra confluence in Brixton (less than one mile away). The slopes of Brockwell Park are on the left, and those of Herne Hill behind the buildings on the right.
d) Summary: Ten key Effra influences on Dulwich: (1) In its upper reaches springs steepened the slopes, made the clay soils waterlogged and unstable, encouraged woodland rather than occupation, and made access difficult - hence a barrier to movement. (2) Roads heading south out of London found it easier to skirt the steeper slopes of the rim of the Effra Basin, following the Thames terraces where possible, and therefore by-passing Dulwich. Because there were few people and therefore little need for access south of Dulwich (at least until the Crystal Palace was built), College Road was never publicly maintained: it was only improved by an early 19th century Penge grazier to give him access to land leased from the College - hence London's only surviving Toll Gate. (3) East-west road connections in Dulwich were limited until quite recently to Court Lane (from the Lordship Lane turnpike), and Burbage Road and Half Moon Lane to Herne Hill - significantly following the general slope of the Effra basin. Dulwich Common was effectively just a local lane until th new Dulwich College was built in the 1870s, carrying very little traffic. The present South Circular Road was an ill-considered product of 1940s planning policies, whose principal modern legacy is a perpetual stream of through traffic which effectively cuts Dulwich in two. There wasn't a bus route through the Village or along the Common until the 1960s. (4) The railways had to be raised above the Thames and Effra floodplains on viaducts (whose arches provided workshops and cheap dwellings for the working classes). They then skirted the Dulwich meadows on embankments, and cut through the steepest slopes by means of expensive cuttings and tunnels, as at Crystal Palace and West Norwood. A particularly interesting case was the 'High Level' Railway that followed the rising Effra watershed for just three miles from Nunhead to Paxton's 'Crystal Palace': it had to tunnel twice through the winding ridge at Sydenham Hill to reach its over-elaborate terminus. With few residents or businesses along it, it could hardly have been viable even in the Palace's Victorian heyday. (5) Although close to Central London, the air in Dulwich was relatively clean and unpolluted. This was because Dulwich was upwind (west and south-west) of the heavily polluted industrial areas of Thames-side and the East End. It was therefore recognised early on as a valuable 'green lung' for London: Dulwich Park was a direct outcome, and it is still enshrined in Southwark's planning policy. (6) The steep north-facing slopes to the south encouraged rapid water movement and cold air drainage into the Dulwich basin, increasing the incidence of fog, frost and dew on Dulwich Common. (7) The combination of decreasing slopes, clay soils, high water table, and cool damp climate encouraged the water meadows which originally gave Dulwich its name, as well as its prevailing green appearance and leafy environment. These conditions encouraged grazing rather than crop-growing, but once drained the clay soils and gentle slopes proved ideal for allotments, parks, gardens, and playing fields. (8) The environment also later encouraged the successful planting of a wide variety of imported trees and shrubs, providing another of Dulwich's defining characteristics - especially its horse chestnuts, cedars, and plane trees. As a result of the high water table, Dulwich has one of the highest densities of ponds and water features in London, which provide distinctive habitats for wildlife, all additional attractions to both residents and visitors. (9) The site, form and fabric of Dulwich Village itself also owes much to the river: the original settlement was on the low terrace just to the east of the Effra flood plain, the wealthier houses and the Old College were built overlooking the river, and storm ditches alongside College Road became today's wide grass verges. (10) Most of the older buildings used local materials, eg timber and charcoal from the Great North Wood, reeds, withies and tiles from Dulwich Common, and the distinctive yellow London Clay bricks from Sydenham Hill and Upper Norwood, and from Dawson's Hill in East Dulwich.
In summary, it can be seen that the Effra Basin's location and natural environment have combined with historical precedent, planning and management policies, and market forces to make Dulwich a particularly desirable place to live, for those willing and able to pay for the privilege, all of which is reflected in its current economic and social geography.
e) The Effra and Dulwich: past, present and future:
In ancient times the valley of the River Effra directed Stane Street from the Channel coast and the Weald towards the first Thames crossing at Thorney Island (now Westminster). In Tudor times it gave access to fresh air, forest resources and foodstuffs for the English Court, London's wealthy merchants, and the growing population that serviced them. In the 18th and 19th centuries Lambeth and Southwark became important dormitories for London, while in recent times the Effra basin has increasingly nurtured educational, cultural and leisure opportunities for a wider community. Dulwich is now known and appreciated for the distinctive quality of its social, cultural and residential environment, all of which owes much to its earlier Effra connections. But what of the future?
The recent announcement that 'Lambeth's lost river' is to be uncovered again for environmental reasons is certainly ironic, since it was sent underground in the first place largely because of its contribution to South London's chronic flooding and water-borne disease problems! The Effra will never return to its former commercial importance of course, but experience from the successful reclamation of former polluted water areas in Docklands and elsewhere offers hope that the environmental benefits may lead to some improvements in residential status and desirability in presently disadvantaged parts of Lambeth, through the spread of some of those characteristics that gave Dulwich its unique quality.
Will climate change resulting from global warming alter Dulwich's character?
Will Brixton become the new Dulwich?
For further information, contact martindknight@gmail.com