"The reduction in the growth rate will be manageable. It will be less than even one percent...about 0.5 percent," said W.A Wijewardena, deputy central bank governor.
The bank said the tsunami would hit economic output after damaging tourist resorts, wiping out fishing fleets in some areas and destroying infrastructure such as roads and railway lines.
Tourism and fishing together account for around 3.0 percent of gross domestic product, and the main industrial hub near Colombo on the west coast was relatively unscathed.
The Central Bank has forecast the economy will grow 5.0-5.5 percent in 2004. It did not provide a forecast for 2005.
The Finance Ministry targeted 6.0-8.0 percent growth for 2005 prior to Sunday's tsunami, which has killed over 28,500 people in Sri Lanka and left more than 5,000 missing.
"If we use the disaster as an opportunity to rectify some of the regional shortcomings we had once and for all, then the disparity should go down," said Anila Dias Bandaranaike, head of the bank's statistics department.
Sri Lanka's road and rail infrastructure is in disrepair, a legacy of years of under-funding as the government channelled resources towards its two-decade war with Tamil Tiger rebels.