Geomorphological and historical data of the lower course of the Perak River (Dindings
B.N. Koopmans published this interdisciplinary study in 1964, combining a 1962 geo-hydrological field survey of the Dindings area in Lower Perak with a systematic analysis of historical maps of Malaya spanning 1667 to 1881. The central argument is that the Perak River shifted its course multiple times during historical times, and that the “Island of Perac” depicted on European maps for over three centuries was a persistent cartographic error with no geomorphological basis.
Summary
Koopmans identifies five distinct old river courses (I–V) in the Dindings lowland through aerial photograph interpretation and field observation, establishing a sequence of river migration from north to south over historical time. The oldest course (I) flowed past Bruas directly to the sea and predates the Kingdom of Bruas itself. A slight rise in sea level enlarged the Dindings estuary, which at its maximum extent in the 14th–15th centuries reached as far as Bruas, allowing ships to anchor in a harbour approximately 2 km southwest of the town. When the Perak River shifted to a more southerly position (Course II), the estuary began to silt up, a process that culminated in the decline of Bruas around 1511. Subsequent shifts produced Courses III, IV, and V, the youngest of which still show natural levees of 1–3 m height and oxbow remnants indicating prolonged occupation of those channels.
The historical map analysis reveals that the “Island of Perac”—purportedly formed by the confluence of the Perak and Bruas Rivers—appears on virtually all European maps from Blaeu (1667) through Tassin (1840), yet is conspicuously absent from Captain Thomas Forrest’s 1792 map, which is the only one to accurately depict the lower Perak River inland to the Kinta confluence. Koopmans argues that the island never existed in the form drawn; the maps inherited and perpetuated an error originating in the earliest attempts to chart the impenetrable interior. The coastline itself has also changed markedly: mangrove encroachment has advanced approximately 1 km over 80 years near Pantai Remis, and the Bruas River mouth has shifted from north to south of that village since 1879.
The synthesis section ties the geomorphological and cartographic evidence together, demonstrating that beach ridges formed after the rivers abandoned their courses, that groundwater salinity patterns confirm recent landward encroachment over former sea, and that the smaller islands shown on historical maps south of the “Island of Perac” correspond to the braided channels of Courses IV and V, which no longer exist in that configuration.
Key Findings
- Five old river courses (I–V) were identified from aerial photographs; Course I (past Bruas) is the oldest, while Courses IV and V are the youngest, showing natural levees of 1–3 m and oxbow remnants (pp. 177–180).
- Alluvial deposits over bedrock are generally ~100 m thick, reaching approximately 200 m where buried channels occur near the 58½ milestone on the Simpang Ampat–Sitiawan road (p. 177).
- Old beach ridges lie 3–6 m above mean sea level, 400 m inland from the present coast, and extend up to 19 km inland near Badak River; sand is well-sorted, coarse to very coarse, with ~90% of grains between 0.25 and 1 mm (pp. 180–181).
- Mangrove encroachment near Pantai Remis is estimated at approximately 1 km over 80 years, consistent with Linehan’s figure of 800 m in 50 years for the Perak–Province Wellesley coast (p. 183).
- The “Island of Perac” appears on maps from Blaeu (1667), Valentijn (1726), Mortier (1740), d’Orleans (1752), Mannevillette (1775), and Tassin (1840), but is absent from Forrest’s 1792 map, which accurately charts the lower Perak to the Kinta confluence (pp. 183–185).
- Remnants of an artificial harbour (U-shaped, angular extension) were detected on aerial photographs southwest of Bruas between Kg. Pulau Merenti and Kg. Gelong (grid ref. 505597), supporting the historical record of Bruas as a port (p. 186).
Conclusion
Koopmans concludes definitively that the “Island of Perac” was a cartographic fiction propagated across more than three centuries of European mapmaking, and that the true history of the lower Perak is one of progressive southward river migration, estuarine silting, and coastal progradation that destroyed the harbour of Bruas and transferred maritime importance to the Perak River mouth by the late 16th century.
Context
- Primary archival sources include the collection of historical maps of Malaya held in the Geography Department, University of Singapore, and a smaller collection in the Geography Department, University of Malaya, supplemented by 1957 geophysical survey data from the Overseas Geological Surveys and borehole records from P.W.D. (Perak) (pp. 177, 182).
- The study contributes to the historiography of Perak by providing the first geomorphological verification of Winstedt and Wilkinson’s (1934) hypothesis that Bruas’s decline was caused by estuarine silting, and by demonstrating that the cartographic tradition of the “Island of Perac” was an error rather than a reflection of a real geographical feature.