Flood Plains National Park

Lore & Background

The park lies in the dry zone of Sri Lanka, receiving a north-east monsoon from October to late-January, followed by a dry season from March to September. The Mahaweli River flows through its center, and the villus—around 38 recorded—are inundated both in wet and dry seasons due to the river's headwaters experiencing the south-west monsoon. Historically, before river diversion for irrigation, these villus served as important dry season grazing grounds. The park's elevation ranges from 20 to 60 metres, with sparse rock outcrop and rich alluvial soil.

Reader's Guide

Flood Plains National Park is significant for its role in elephant conservation within the Mahaweli catchment, providing a corridor for elephants migrating between Wasgamuwa and Somawathiya national parks. Together with Somawathiya, it offers sanctuary for resident and migratory waterfowl, with around 75 species wintering in its swamps. The park's villus system supports high net primary productivity and a diverse array of flora and fauna, including rare species like the lesser adjutant and grey slender loris. However, the park faces threats from dam construction reducing flood duration, invasive alien species such as Eichhornia crassipes, and harmful activities like kiln holes causing elephant deaths. It was added to the 1989 IUCN/CNNPA register of threatened protected areas due to resource overexploitation, and management has been hampered by political and security issues. No specific management plan exists for the park; it is treated administratively as part of Somawathiya and Wasgamuwa national parks.

Did You Know?

• The park contains around 38 shallow swampy depressions called 'villus'.
• An ancient cave monastery with inscriptions from between the 2nd and 7th century BC was found on the right bank of the Mahaweli River at the edge of the Mutugalla villu.
• The park is one of the recorded habitats of the grey slender loris (Loris lydekkerianus).
• About 25 plants of the rare herb Pentapetes phoenicea are found at three sites in the marsh forest.

Geography & Physical Landscape

Horton Plains sits atop the southern edge of Sri Lanka's central highland plateau, where elevations climb from roughly 1,200 metres to 2,300 metres above sea level. To the west and north stand the island's second- and third-highest summits, Kirigalpoththa at 2,389 metres and Thotupola Kanda at 2,357 metres, framing the plateau like ancient sentinels. The bedrock beneath the grasslands is remarkably old, belonging to the Archean and Precambrian eras, and is composed of khondalites, charnockites, and granitic gneisses. Soils fall into the red-yellow podsolic group, their surface layers thick with decayed organic matter. The climate is cool and wet. Average annual rainfall exceeds 2,000 millimetres, and persistent cloud cover chokes off much of the sunlight that reaches the ground. The mean annual temperature hovers near 13 °C, yet daily swings are dramatic: daytime highs can touch 27 °C while nighttime lows dip to 5 °C. Ground frost is a regular February occurrence, and during the southwest monsoon the wind can gust to gale force. In the wet season, dense mist can hang over the plateau for most of the day.

Hydrology & Water Features

Few landscapes in Sri Lanka carry as much hydrological weight as Horton Plains. The plateau serves as the headwater source for three of the island's principal rivers—the Mahaweli, the Kelani, and the Walawe—making it the country's most critical drainage basin. Beyond those three, the plains also give rise to the Belihul Oya, Agra Oya, Kiriketi Oya, Uma Oya, and Bogawantalawa Oya, threading water across a vast stretch of the island. The terrain itself is studded with pools, streams, and waterfalls. The most dramatic feature is World's End, a sheer precipice that plunges 870 metres into the valley below. Baker's Falls, a 20-metre cascade carved by the Belihul Oya, a tributary of the Walawe, was named in honour of the explorer Sir Samuel Baker. Slab Rock Falls adds another notable drop to the collection. In the lower-lying hollows, waterlogged swamps and sluggish streams support a distinctive community of aquatic macrophytes, including Aponogeton jacobsenii, floating sedges, and bladderworts, while the dense bamboo Chimonobambusa densifolia lines the stream banks.

Flora & Biodiversity

The park's vegetation splits into two broad communities: roughly 2,000 hectares of wet patna, open montane grasslands and shrublands, and about 1,160 hectares of subtropical montane evergreen forest. Together they harbour close to 750 recorded plant species spanning 20 families. The forest canopy climbs to around 20 metres, dominated by Calophyllum walkeri and interwoven with Myrtaceae and Lauraceae members. Beneath that canopy, thickets of Strobilanthes form a dense undergrowth that effectively suppresses any herb layer, while dwarf bamboos and Rhodomyrtus tomentosa bushes colonise the margins and peaks. Of the 54 woody plant species documented in the park, a remarkable half are endemic to Sri Lanka. The grasslands, shaped by recurring fire and grazing, are led by Arundinella villosa and Chrysopogon zeylanicus. Horton Plains also shelters large herds of Sri Lankan sambar deer and has been designated an Important Bird Area, hosting numerous species found nowhere else on the island and several restricted to the plateau itself. It holds the largest remaining expanse of cloud forest in Sri Lanka.

History & Conservation

Long before it bore a European name, the plateau was known locally as Maha Eliya Thenna, meaning 'great open plain.' In 1834, Lieutenant William Fisher of the 78th Regiment and Lieutenant Albert Watson of the 58th Regiment are credited with 'discovering' the plateau, and it was subsequently renamed for Sir Robert Wilmot-Horton, the British governor of Ceylon from 1831 to 1837, who had visited the area in 1836 to meet the Ratemahatmaya of Sabaragamuwa. Stone tools linked to the ancient Balangoda culture have been unearthed on the plains, and lowland communities once climbed the mountains to mine gems, extract iron ore, build irrigation canals, and fell timber. Conservation efforts began in earnest after botanist Sir Joseph Dalton Hooker urged the British government to leave montane forests above 5,000 feet untouched, leading to a protective administrative order in 1873. The area was formally declared a wildlife sanctuary on 5 December 1969 and elevated to national-park status on 18 March 1988. In July 2010, the broader Central Highlands of Sri Lanka, encompassing Horton Plains, the Peak Wilderness Sanctuary, and the Knuckles Mountain Range, was inscribed on the UNESCO World Heritage List.