THE SEA DEFENCES OF BRITISH GUIANA. 



By H. Siccama. 



At the time that the alluvial soil forming the coastlands of Guiana 

 was deposited, the circumstances were different from those at present 

 prevailing. The flood currents approached the coast from the north- 

 east instead of from the south-east, as they do now. This is indicated 

 by the direction of all the old estuaries, which opened their entrances to 

 the north-east, whereas now they are all slewing round to the south- 

 east. 



While the alluvium was being deposited the mean sea-level must 

 have been lower in relation to the land, as otherwise the shell reefs and 

 sand ridges must have been higher to form a reticule of lagoous where 

 fresh-water plants could exist and flourish and aid in the general rise of 

 the surface. Most of those reefs and ridges are below the present high- 

 water level and would be overflown it high tides if it were not for the 

 sea-dams, such as they are. What this means can be seen on the east 

 coast of Berbice, where what were at one time cultivated lands are now 

 brackish swamps. 



Most likely too the dry land must have extended very much further 

 seaward than the coast-line as it appeared when the first settlers arrived 

 in the Guianas. The first depths of their plantations were then laid well 

 back from the coast-line, so that their sea-dams were protected from 

 surf by the courida and other trees left in front. 



What the reason may be for the encroachment by the sea is difficult 

 to determine in the absence of trustworthy information. It may be due 

 to a slow oscillation of the earth's crust, as is the case in other parts of 

 the world, through which the surface of the ground sinks with regard to 

 the mean sea-level. It may also be that while the alluvial ground was 

 deposited the form of the sea-bottom far out at sea was different, so that 

 the coast of the mainland was more sheltered than now from heavy seas 

 and there existed a bay between headlands — that to the north Trinidad 

 and to the south Cayenne. 



Whatever the state of things may have been many centuries ago 

 cannot be ascertained with the information at our disposal. We only 

 know that the coast-line is everywhere eroded, not so much by littoral 

 currents like on the east coast of England and the west coast of Holland 

 and Belgium as by the action of the surf, locally called the wash. 



This wash does not act with the same energy all along the coast- 

 line, but intermittently. Sometimes it is bad at one spot, in other years 

 at another. It may be that where there is a temporary rest of the wash 

 such a spot may at the time be more or less protected by banks travel- 



