Master Plans and Area Plans

A master drainage plan addresses the current and future drainage needs of a given community. The boundary of the plan usually follows regional watershed limits. The proposed facilities may include channels, storm drains, levees, basins, dams, wetlands or any other conveyance capable of economically relieving flooding problems within the plan area. The plan includes an estimate of facility capacity, sizes and costs.

MDP's are prepared for a variety of purposes. First, the plans provide a guide for the orderly development of the County. Second, they provide an estimate of costs to resolve flooding issues within a community. These plans are used by the District's Management, Zone Commissioners and Board of Supervisors to determine Capital Project expenditures for each budget year. Finally, the plans can be used to establish Area Drainage Plan fees for a given community, which prevent existing taxpayers from having to shoulder the burden of land development costs.

An area drainage plan is a financing mechanism used to offset taxpayer costs for proposed drainage facilities. The fees are imposed on new development within the plan area. The Subdivision Map Act requires that agencies imposing fees have a general drainage plan for the fee area, a special fund for the fees and an equitable distribution of the fees prior to implementation. The Area Drainage Plan is essentially the Master Drainage Plan with additional language supporting the costs and distribution of the fee within the plan area. Developments falling under the Subdivision Map Act (those requiring a division of lands) pay fees on a per acre basis. Developments falling outside of the Subdivision Map Act (known as discretionary developments) can only be assessed fees based on their impacts to the watershed. The ADP Rules and Regulations state that these impacts can be related to the amount of impervious surface area that the development creates. Therefore, discretionary developments are charged not on a gross acreage basis, but on the total impervious acreage created by their development. The ADP Rules and Regulations establish guidelines used in the administration of ADPs including design and construction responsibilities and fee credit determination.