Your council will have a policy on the deployment of sandbags in your area. Some will have a service that provides them, some won’t, whilst others will be discretionary.
If they do provide them, they may deliver them to the area or you may have to collect them from a depot. There may also be a limited supply.
It’s worth finding out what your council’s policy is so that you can plan what you might need to put in place.
Consider buying alternative sandbags that you can keep on your property. It will mean that they are immediately there when you need them.