Full text: Transactions of the Symposium on Photo Interpretation

south of the lagoon so that the transported material may act as an additi 
onal feed to the longshore currents. It is very probable that the lagoon 
waters may turn brackish because of this. These brackish conditions may 
adversely affect the fish life which is the main food supply of the area. There 
fore, the economic repercussions of this proposal must be considered 
5. It will be worthwhile studying the effect of a dam built in the sea at the 
cape in the direction of the bar. This will act as a breakwater but at the 
same time will have the disadvantage that it will prevent sand from reach 
ing the coast. To determine which is more advantageous is a problem 
requiring more detailed investigation. 
Before these recommendations are executed it is imperative that a thorough 
field and laboratory study should be undertaken to determine the effects they 
would have on the coast. The Hydrology Department could do this by building 
a model of the area and subjecting it to the conditions prevailing there. Then 
a more definite idea can be obtained of the extent to which the proposed 
structure will be beneficial or not. 
6. Artificial nourishment is often preferred to dams and walls for protecting 
beaches in many parts of the world, due mainly to the following reasons: 
a. The direct method of improving beaches is by replacing the eroded 
b. Nourishment, either artificial or natural, does not have the same adverse 
effects as structures on beaches. Groins and walls create problems of 
accelerated erosion on their leeward side with little protective influence 
on the windward side. More and more recognition is being given to 
the fact that preventing erosion by means of such protective structures 
may often be a dangerous practice, because in many cases such pro 
tection is obtained at the expense of producing or expanding a problem 
c. Provided that a sufficient amount of suitable material is available, 
nourishment will improve the natural beauty of the beach. 
d. This method not only benefits the shore on which it is placed, but also 
the adjoining shores. It is usually less expensive than artificial struc 
Churning of the lagoon deposits during the ebb-tide would accelerate the 
amount of sand sucked out of the lagoon, and thus would result in increased 
sedimentation offshore of Negombo. This method will probably not have 
adverse effects on the fisheries in the lagoon, as mentioned under heading 4. 
Filling material could also be obtained by pumping with a hydraulic 
dredge either from the bay or from the off-shore area. However, a study should 
be carried out to find whether the available material is suitable and if it 
can be obtained at a reasonable cost.

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