Flood control operations such as the ones financed by an assessment district provide special benefits. Flood control infrastructure protects particular identifiable parcels from flood damage, and the benefits are provided directly to those parcels and to none other. This means that an assessment can only be levied onto those properties which benefit directly from the improvements.
In the case of the South Bayfront Levee Improvements, the project cost of $7.5M was spread over the 8,000 parcels that receive the direct benefit of protection from tidal flooding, resulting in a relatively low cost per owner.
The remaining flood improvement projects in other areas of the City are relatively more expensive when considering the number of property owners who would share the burden. This makes the formation of additional assessment districts unpractical and in some areas would cost more than flood insurance.