Part of the South Coast line is closed and some road links are operating at limited capacity.

Land slips at Scarborough and Wombarra and flooding at places like the Port Kembla station have damaged the South Coast line.

"The South Coast line between Waterfall and Bomaderry is closed due to damage along the line," Sydney Trains Chief Executive Matt Longland said.

"Buses are replacing trains in both directions between Waterfall to Bomaderry, inclusive of Wollongong to Port Kembla."

On the road, the major damage occurred near the Sea Cliff Bridge and Transport for NSW Chief Customer Officer Roger Weeks said that would be open in a limited capacity.

There would be one lane on Lawrence Hargrave Drive reopened under 'stop and slow' conditions between Coalcliff Station and Clifton School Parade.

"As we continue to undertake assessments, we will have a clearer understanding of the amount of work and time required to fix the road," Mr Weekes said.

"We thank motorists for their patience and understanding during this process. We are working as quickly as we can to fully reopen the road."