ARCDBA.TierII_Catchment_MDE_Py

The Clean Water Act requires three components to water quality standards that set goals for and protect each States' waters. The three components are: (1) designated uses that set goals for each water body (e.g., recreational use), (2) criteria that set the minimum conditions to support the use (e.g., bacterial concentrations below certain concentrations) and (3) an antidegradation policy that maintains high quality waters so they are not allowed to degrade to meet only the minimum standards. The designated uses and criteria set the minimum standards for Tier I. Maryland's antidegradation policy has been promulgated in three regulations: COMAR 26.08.02.04 sets out the policy itself, COMAR 26.08.02.04-1, which is discussed here, provides for implementation of Tier II (high quality waters) of the antidegradation policy, and COMAR 26.08.02.04-2 that describes Tier III (Outstanding National Resource Waters or ONRW), the highest quality waters. No Tier III waters have been designated at this time. Tier II antidegradation implementation has the greatest immediate effect on local government planning functions so MDE has prepared this set of Tier II GIS data layers to provide technical assistance to local governments working to complete the Water Resources Element of their comprehensive plans as required by HB 1141. As part of this process, MDE has created a catchment dataset representing the general land area that can directly affect that Tier II stream's segment water quality via run off. The publicly maintained list of all Tier II waters and for further information regarding Maryland's High Quality Waters, Tier II, please visit http://www.mde.state.md.us/ResearchCenter/Data/waterQualityStandards/Antidegradation/index.asp

The intended use of the catchment dataset is to assist State, Local, and Federal officials and stakeholders in determining the antidegradation status of current or planned activities which fall under the purview of the antidegradation policy and implementation procedure (COMAR 26.08.02.04-1). Using GIS, the stakeholder can assess if any activity, proposed or operational, such as a discharge, is located on land which drains (has run off) directly into and can potentially adversely affect a Tier II stream segment. This type of determination would be useful for permitting purposes, screening for sensitive or high quality resources, and various land use planning activities such as those undertaken by local officials during the Water Resources Element process, Water and Sewer Planning, or the Comprehensive Planning process. The catchment watersheds were delineated using the 30 meter digital elevation models (DEM) acquired from the United State Geological Survey (USGS). The placement of each catchment was based on the list of all identified Tier II segments which includes those stream segments promulgated in the Code of Maryland Regulations COMAR 26.08.02.04-1, and those additional segments proposed during the current Triennial Review of Maryland Regulations, known as the pending list. Pending segments are Tier II segments awaiting promulgation. This dataset is intended to be used in conjunction with the other official Tier II MDE datasets: Tier II Stream Segments , Tier II MBSS Stations, and Tier II Stream Endpoints. The publicly maintained list of all Tier II waters can be found for each county at the following website: http://www.mde.state.md.us/ResearchCenter/Data/waterQualityStandards/Antidegradation/index.asp

For accuracy National Hydrology Dataset stream coverages (24K), topographical maps, and MDE generated Tier II stream segment delineation layers. Where appropriate and necessary boundaries were manually moved using best professional judgement based on information provided by the tools listed segment, the boundary was manually expanded to include the missing segment or vice versa.

Not Applicable