458 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
Fig. 4 
SW = Amount of material brought by 
the predominant south-west 
monsoon. 
S — Amount of material leaving the 
area due to northward drift, 
(small amounts, due to limited 
length of fetch). 
N = Net amount of littoral drift 
material entering the area from 
the north (north-east monsoon). 
P = Amount of material sucked into 
the lagoon with the rising tide. 
T = Amount of material sucked out 
of the lagoon during the ebb 
current. 
R = Amount of material brought by 
the river. Most of it is deposited 
on the southern part of the 
lagoon. 
position. The position of these beach ridges, coupled with the northerly plung 
ing bar and the consequent absence of a lagoon, indicates a tilt in this area due 
to some tectonic movement. It should be noted in this connection that an 
airborne geophysical survey revealed the presence of a major fault in the 
Negombo area. The possibility that this influenced the coastal developments, 
cannot be excluded. 
Recommendations for coastal protection 
Keeping in mind that the main purpose of this study is to protect the coast 
near Negombo town, a few recommendations can be put forward. 
1. Extension of a bulkhead construction along the established bulkhead line 
in stages as required to protect property endangered by erosion. No dams 
should be built on the north side of Negombo so that there may be free 
southward longshore transportation of sand (N in fig. 4). 
2. The established bulkhead line should be the focus of all future bulkhead 
construction and the seaward limit of all building construction. 
3. Definite measures should be taken to prevent any hindrance to the supply 
of littoral drift sand reaching the developed area from the south and south 
west of Negombo. 
4. Closing the outlet of the lagoon may have the following results. It would 
prevent sand from being sucked into the lagoon during the rising tide, 
thus concentrating the accumulation on the seaward side of the outlet and 
in front of Negombo town. This would have a protective effect on this part of 
the coast. An outlet should be built for discharging the water of the lagoon 
to the south. It may also be possible to divert the course of the river to the