This question ultimately depends on the cause of the flooding and what is stated in the tenancy agreement between the landlord and the tenant.
Unless otherwise stated, tenants will typically be responsible for maintaining drains and faucets. Similarly, landlords will most likely be responsible for maintaining the structure and exterior of the building, including external gutters, drains and pipes.
If the source of the damage arises from the landlord's obligations, such as due to structural issues that has caused leaks from the roof, they are responsible for repair. However, it is unlikely they are responsible for any damage to a tenant's belongings. It is highly recommended that tenants acquire contents insurance because even if the damage has arisen from the landlord's repair responsibilities, any damage to contents is unlikely to be their responsibility.
Read more about repairs in rentals.