Some 300 years before the first Mandovi Bridge was built (1971), there existed a magnificent structure in the form of a low passageway in the vicinity: the landmark Ponte de Linhares. Linking Patto to Ribandar, popularly known as the Ribandar causeway, it has been acclaimed as an engineering wonder of yesteryears. Historical documents are replete with eloquent descriptions of this heritage structure. The classic “A India Portuguesa” (1886) by Antonio Lopes Mendes, explorer, agronomist, illustrator and cartographer has candidly described it all.Considering that the bridge is in dire straits, modern historians have strongly supported its restoration.
The causeway in fact comprises a low bridge, 2.6 km long with 40 pillars, built with large laterite blocks, and reinforced with wooden beams. It was built across a former saline marshy stretch which constituted the Mandovi backwaters, creeks and lagoons, an expansive wetland that extends up to Merces – Santa Cruz villages. River water entered the wetland through three main passages: Ourem creek, Ribandar creek and a third creek located midway. Men in canoes used to enter through these under-passes.It appears that this structure was never maintained ever since it was built.
A close analysis of the Survey of India (SoI) toposheets of 1964 reveals that a kilometre wide strip abutting the entire causeway consisted of salt pans, interspersed within low paddy fields. Coconut trees were the dominant tree species. Mangroves were totally absent along the river, not identified even within the narrow creeks. Similarly, the National Hydrographic Office (NHO) charts of 1970 and 1986 confirm that the Patto-Ribandar causeway traversed extensive salt pans, and was entirely free of mangroves. Several historical documents also testify this observation.
Over the decades however, the passages under the 40 archways have been blocked due to siltation. A large mud flat has accreted along the river front and this clayey deposit is advancing further into the river.Today, a newcomer may not find evidence that this causeway is indeed a bridge.Presently, the entire area constitutes an intricate system of lagoons (former salt pans) influenced by daily tides and heavily invaded by thick mangroves. These trees obviously started proliferating rapidly during the last 30-35 years. As such, the heritage causeway stands clutched by dense mangroves.
Historian priest Visitação Monteiro has already elaborated the precarious condition of the causeway.A close look at the base of the walls on either side indicates that the roots of the mangroves are interfering with and have penetrated the base, and consequently the foundations of the causeway. This is probably one of the reasons why the roadway is weakened and is collapsing or sinking. Multi-dated Google Earth (GE) images and a walk by the river side give a clear evidence of the closeness of mangrove trees with regard to the bridge. At a particular place, dense mangroves have entirely engulfed the ancient bridge over a stretch of 460 metres.
As a member of the GCZMA, this author had reported the threat to the causeway by haphazard mangrove growth during the 125th GCZMA meeting held on February 11, 2016. After discussions and due deliberations, the authority decided to refer the matter to the Department of Forests for a detailed study. Subsequently, the GCZMA received a letter dated May 4, 2016 from the Principal Chief Conservator of Forests clarifying the various issues raised by this author in his report of February 9, 2016. These comments and a further reply will form another article. This author asserted that the topic requires proper examination as the causeway is a heritage structure worth preserving. In the 130th meeting on June 21, 2016, the GCZMA then decided to request the Archaeological Survey of India, Chief Conservator of Forests and Chief Engineer, PWD, to conduct a scientific study and to submit their findings. Alas, the study never came.
The Forest Department has planted mangroves in the river along the causeway. Although the intentions of these plantations cannot be doubted, the approach adopted is totally wrong. These trees have been planted too close to the stone walls. Apparently, the authorities concerned are not even aware of what this heritage structure is all about.It may be noted that mangrove cover in the state of Goa has increased rapidly. Analyses by Space Applications Centre (SAC), Ahmedabad, have revealed that the surface occupied by mangroves in Goa has increased from 6 sq. km to about 24-28 sq. km. in about three decades. Unfortunately, since a robust mangrove policy is lacking, mangroves are functioning as opportunistic immigrants of soft soils. These trees are thriving where they should not grow (salt pans, paddy fields, lagoons), but instead, are vanishing from their rightful places where they ought to sustain (creeks, river banks).
Our forest officials have no qualms in uprooting 700 mangroves for the new bridge; but relocating a narrow strip for the sake of a heritage bridge appears daunting! It is strongly suggested that the mangrove trees which are too close to the edges of the causeway be removed and transplanted.
All the plants within this ‘setback’ need to be removed forthwith. In brief, our fabled Ponte de Linhares is an engineering wonder of yesteryears, a structure of archaeological and historical relevance, and hence calls for protection and conservation at all costs. Impacts from natural and anthropogenic forces need to be curtailed. The causeway of yore needs to endure its inimitable identity.
(Dr Antonio Mascarenhas is a former Scientist, NIO, Goa)
