|Originator||Minnesota Geospatial Information Office (MnGeo) for the Minnesota Pollution Control Agency|
|Title||Statewide Altered Watercourse Project|
|Abstract||The Altered Watercourse Project was a joint effort between the Minnesota Pollution Control Agency (MPCA) and Minnesota Geospatial Information Office (MnGeo) to create a statewide inventory of streams that have been hydrologically altered (e.g. channelized, ditched or impounded). The dataset was created to support MPCA's water quality monitoring and assessment program and provides information about stream habitats that have been compromised through such alteration.
The project entailed digitization of Geographic Information System (GIS) 'events' on to the United States Geological Survey's National Hydrography Dataset (NHD) stream linework. The events were then categorized as one of four types: Altered, Natural, Impounded or No definable channel, based upon a standardized methodology and criteria. These categorizations were performed manually by GIS technicians using visible interpretation of multiple years of aerial photography, LiDAR (Light Detection And Ranging)-based elevation data, and various other reference data in ArcGIS 10.0.
|Purpose||This project is being conducted in support of the MPCA's water quality monitoring and assessment program. Specifically, the MPCA is developing a refined use designation process known as 'Tiered Aquatic Life Use' (TALU) to account for situations in which stream habitat has been compromised through hydrological alteration. An accurate state-wide determination of altered streams will assist in the assignment of the correct beneficial use within this new TALU framework.|
|Time Period of Content Date||2013|
|Currentness Reference||Altered Watercourse determinations were referenced to NHD flowlines vintage 2012 or 2013, using ancillary data including the newest available aerial imagery and LiDAR-derived elevation.|
|Maintenance and Update Frequency||Unknown|
|Spatial Extent of Data||Minnesota, Statewide|
|Theme Keywords||inlandWaters, hydrography, national hydrography dataset, NHD, NHD events, altered watercourse, altered streams, natural streams, channelized streams, rivers, ditches, impoundments, Tiered Aquatic Life Use (TALU)|
|Theme Keyword Thesaurus||ISO 19115 Topic Category|
|Access Constraints||To be determined|
|Use Constraints||None, but users should consult the project methodology document for an understanding of the derivation, uses and limitations of the data set.|
|Contact Person Information||Scott Niemela,
Princial Pollution Control Specialist|
Minnesota Pollution Control Agency
7678 College Road
Brainerd, MN 56425
|Browse Graphic||None available|
|Associated Data Sets||The high-resolution National Hydrography Dataset (NHD) NHD flowline feature class provided the linework upon which the altered watercourse determinations were created.|
|Section 2||Data Quality|
|Attribute Accuracy||Interpretations were based on the methodology document identified in the 'Lineage' section. The methodology and decision tree with criteria was set up to provide a systematic and repeatable way of making these determinations. Checking tools could test for internal consistency of the determination, but not for its correctness. The MPCA review process was initiated to help ensure that the determinations were correct. Not all of the newest data layers were available at the right time for all locations, and there is certainly still an element of interpretation in this process. About 7% of initial edit features were identified as needing correction in the MPCA review process, and of those, about 5% resulted in disagreementsbetween the original coder and the MPCA reviewer, and were followed up with a final review.
The landscape is constantly being modified, newer imagery may be available the next time a stream is reviewed, and field visits may also result in determinations being amended. An update process will be developed after the completion and publication of the 6/30/2013 dataset.
|Logical Consistency||Each of the 80 HUC-8s of events underwent a Continuity Check using the USGS Hydrography Event Management (HEM) tool that entailed the finding and fixing of missing events as well as gaps and overlaps between events. These Continuity Checks were done after the Initial, Correction and, if necessary, Final Edit Phases of the project.|
|Completeness||Complete for the state of Minnesota|
|Horizontal Positional Accuracy||Same as horizontal positional accuracy of the underlying NHD dataset. See NHD dataset-specific metadata for subbasin.|
|Vertical Positional Accuracy||Not Applicable|
|Lineage||To fulfill MPCA's water quality reporting requirements, the Altered/Natural Watercourse determinations were defined as Events referenced to the high-resolution National Hydrography Dataset (NHD) flowline feature class. Determinations were developed on data subsets defined by the Watershed Boundary Dataset 8-digit hydrologic Unit (HUC-8) level. There are 80 HUC-8's covering Minnesota. These boundaries are consistent with Minnesota's 'DNR Major Watersheds'. NHD data sets were used for referencing events and were downloaded by HUC-8 as needed from the national NHD repository maintained by the United States Geological Survey. The NHD version date used for the linear referencing activity range from mid-2012 through March 2013. NHD versions for each subbasin are tracked in a project status table. MPCA needs the determinations to be based on the NHD flowlines because all of its water quality reporting to the EPA is based upon the NHD. The NHD internal data types for the flowline category determinations (e.g., stream/river, canal/ditch) could not be used directly because the USGS has different classification criteria. Also, in some cases, it was obvious by comparing the NHD linework with newer imagery that lines categorized in NHD as 'stream/river' based on the 1:24,000 USGS Topographic maps had since been channelized or moved underground.
The Hydrography Event Management (HEM) tool distributed by the United States Geological Survey was used to create the Altered/Natural Watercourse events as continuous line events on the NHD flowline. MnGeo created an 'Altered Watercourse Toolbar' Extension to the HEM Tool that enabled staff to easily add and code additional (non-USGS) attributes: the AW event type, confidence, criteria, NHD update status, and comments.
To begin the process all NHD flowlines within a HUC-8 were selected, and the HEM procedure 'Import Selected flowlines' was used to create a unique event for each NHD flowline feature. The Altered Watercourse tools were then used to add the AW attribute fields to the event file, and to populate these fields based on the methodology. Using the HEM tools the events were split if necessary if parts of an NHD reach needed a different determination (e.g., part natural, part altered). A 150-meter minimum size was specified for individual events - for instance, a natural stream would not be coded as 'altered' for the short distance that it flows through a culvert. Since the underlying NHD is in geographic coordinates, the Altered Watercourse layer derived from the NHD is also in geographic coordinates.
In consultation with MPCA and the Altered Watercourse Advisory Team, MnGeo developed a methodology for making the determinations. The methodology was tested in areas with differing hydrology, and has gone through several revisions. The final methodology document can be accessed at www.mngeo.state.mn.us/ProjectServices/awat/index.htm. The methodology includes a decision flowchart with criteria letters and additional criteria numbers that help describe the decision-making process. Background layers used to help make the determination included: NHD flowlines, areas, and waterbodies; Geographic Names Information System names; DNR dam point locations; background hydrography layers from DNR including Public Waters designations, LiDAR-derived elevation (selected areas);1:24,00-scale DRG's (digital USGS quadrangle maps); and aerial imagery for 1991 (spring, black and white), 2003 (summer - color), and 2006 (summer - color), 2008 (summer), 2009 (summer), 2010 (summer), and, in some areas, spring leaf-off imagery 2009-2011. Additional reference documents were consulted to code stream segments that were difficult to determine. A confidence code for each determination is included in the attribute table.
Based on the methodology, the decision flowchart, and available background information, MnGeo staff created an 'Initial' set of determinations.
QA/QC: Once a HUC was completed, there was an internal QA/QC followed by an external review by MPCA staff.
Internal QA/QC: The Continuity Check function within the HEM tool was used to verify that each flowline in the NHD study area (HUC-8) had been assigned an event, and that there were no gaps or overlaps of events. The only legitimate 'gaps' (lacking an AW event) were for NHD flowlines inside the study HUC's but outside of Minnesota. The Altered Watercourse 'Attribute Check' routine was run. This routine flagged events which were missing any of the Altered Watercourse attributes, or for which the Event Type, Criteria Letter, and Criteria numbers assigned were logically inconsistent. This checker could not determine the correctness of a particular determination.
External QA/QC: Once the HUC was complete and passed all of the internal checks, the data was loaded into the 'AW_INITIAL' layer in the Altered Watercourse SDE database at MnGeo, which was published to a web mapping service. MPCA staff were able to review the Altered Watercourse determinations, viewing the same set of background layers, and using the same methodology and decision chart. For each HUC-8 MPCA provided a 'Review' shapefile, with suggested corrections.
Correction Process: MnGeo staff created a new 'Correction' dataset and, using the MPCA Review shapefile and comments and background information, made corrections to the Initial dataset if they agreed with the correction. If they did not agree, then an event was flagged as 'Disagree' and was set aside for one more round of review by MPCA and MnGeo project leads. The corrected data was loaded into the 'AW_CORRECTED' layer in the Altered Watercourse SDE database at MnGeo.
Altered Watercourse Final Layer: Once the determination disagreements were resolved, the last revisions were made and the HUC-8 was reloaded into the 'AW_FINAL' layer in the Altered Watercourse SDE database at MnGeo. Feature-level metadata, as required by the HEM tool and USGS standards, was applied to the dataset.
Data archive and transfer from MnGeo to MPCA: Data was archived in two formats:
1) 80 HUC-based personal geodatabases for each of the following:"Initial", "Corrected", and "Final"
2) SDE data representing the "AW_Final" and all associated data exported to a statewide file geodatabase.
|Section 3||Spatial Data Organization (not used in this metadata)|
|Section 4||Coordinate System|
|Horizontal Coordinate Scheme|
|Overview||The Altered Watercourse data layer is based on the geometry of the National Hydrography Dataset Flowline feature, and is in the format of the NHDLineEvent Feature Class. The fields from AWEventType through Critnum3 are additional fields that were required to store information specific to the Altered Watercourse Project. Additional data fields are as follows:
AWEvtType - Altered Watercourse Event Type: 1 = Altered, 2 = Natural, 3 = Impounded, 4 = No Definable Channel.
Confidence - Code indicating the confidence level that the staff technician assigned to the AW determination(High, Medium, Low).
NHDUpdate - Code that indicates whether the NHDflowline feature underlying the Event requires updating (1 = None, 2 =Add Feature, 3 = Delete feature, 4 = Change Feature Type, 5 = Change Geometry, 6 = Other).
Notes - Field used to add more information about the determination choice or NHD update required.
Critletter - Criterion Letter describing this determination (A-N) (from methodology document/flowchart).
Critnum1 - Criterion Number 1 describing this determination (1-39) (from methodology document/flowchart).
Critnum2 - Criterion Number 2 describing this determination (1-39) (from methodology document/flowchart).
Critnum3 - Criterion Number 3 describing this determination (1-39) (from methodology
For full data set description see Table Details
|Detailed Citation||Altered Watercourse Determination Methodology, Final Revision 8, Minnesota Geospatial Information Office (MnGeo), June, 2013, p.7
|AW_FINAL - Final Altered Watercourse determinations after all reviews and corrections were applied.|
|Field Name||Valid Values||Definition||Definition Source|
|OBJECTID||Unique ID assigned by DBMS||ESRI|
|COMID||Old Unique Identifier assigned by NHD - no longer used||NHD Data Model - NHDLineEventFC|
|PERMANENT_IDENTIFIER||Unique and permanent identifier assigned to the event by the HEM Tool (Short Form: Permanent_)||NHD Data Model - NHDLineEventFC|
|EventDate||Date the event was created or last modified||NHD Data Model - NHDLineEventFC|
|ReachCode||NHD ReachCode associated with the event||NHD Data Model - NHDLineEventFC|
|ReachSMDate||Reach Version Date - not fully populated in this dataset (Short Form: ReachSMDat)||NHD Data Model - NHDLineEventFC|
|ReachResolution||enumerated||Resolution of the Underlying NHD Dataset (High Resolution NHD was used for the Altered Watercourse project (Short Form: ReachResol)||NHD Data Model - NHDLineEventFC|
|1||Local||NHD Data Model|
|2||High||NHD Data Model|
|3||Medium||NHD Data Model|
|FeatureComID||ComID associated with the NHD Feature that this event is referenced to. Field is obsolete and is not populated. (Short Form: FeatureCom)||NHD Data Model - NHDLineEventFC|
|Feature_PermanentIdentifier||Permanent Identifier of the NHD feature that this event is referenced to. (Short Form: Feature_PE)||NHD Data Model - NHDLineEventFC|
|Feature_ClassRef||NHD Feature Class that holds the Permanent Identifier. (Short Form: FeatureCla)||NHD Data Model - NHDLineEventFC|
|Source_Originator||Organization which developed this data set (Short Form: Source_Ori)||NHD Data Model - NHDLineEventFC|
|Source_DataDesc||Originator's Data Set Name (Short Form: Source_Dat)||NHD Data Model - NHDLineEventFC|
|Source_FeatureID||ID of this feature in source data set. Not applicable to this project and not populated. (Short Form: Source_Fea)||NHD Data Model - NHDLineEventFC|
|FeatureDetailURL||Web Location for information associated with this event (Not applicable to this project) (Short Form: FeatureDet)||NHD Data Model - NHDLineEventFC|
|FMeasure||0 to 100||From Measure - from measure along NHD Reach (% of way along reach)||NHD Data Model - NHDLineEventFC|
|TMeasure||0 to 100||To Measure - to measure along reach (% of way along reach)||NHD Data Model - NHDLineEventFC|
|EventType||NHD Event Type (not applicable)||NHD Data Model - NHDLineEventFC|
|EventOffset||Offset (numeric) of event from Reach (Short Form: Offset)||NHD Data Model - NHDLineEventFC|
|Shape_Length||Length of Event||NHD Data Model - NHDLineEventFC|
|AVEVTTYPE||enumerated||Altered Watercourse Event Type||Altered Watercourse Project|
|4||No Definable Channel||AW Project|
|Confidence||enumerated||Delineation staff confidence in this determination||Altered Watercourse Project|
|NHDUpdate||enumerated||NHD Update type required - flags whether the underlying NHD needs to be updated for this reach||Altered Watercourse Project|
|4||Change FType||AW Project|
|5||Change Geometry||AW Project|
|Notes||Text field for clarification of AW determination or NHD update determination.||Altered Watercourse Project|
|CritLetter||A to N||Criterion Letter - Letter that indicates a combination of Determination Type and Confidence||Altered Watercourse Project|
|Critnum1||0 to 3 Criteria Numbers can be associated with each AW determination (1-9, 11-18 for Altered), (21-27 for No Definable Channel), (31-39 for Impounded)||Altered Watercourse Project|
|Critnum2||0 to 3 Criteria Numbers can be associated with each AW determination (1-9, 11-18 for Altered), (21-27 for No Definable Channel), (31-39 for Impounded)||Altered Watercourse Project|
|Critnum3||0 to 3 Criteria Numbers can be associated with each AW determination (1-9, 11-18 for Altered), (21-27 for No Definable Channel), (31-39 for Impounded)||Altered Watercourse Project|
|Length_KM||Add-on field that holds the length of the event in kilometers.||Altered Watercourse Project|
|Publisher||Minnesota Pollution Control Agency|
|Contact Person Information||Benjamin Lundeen,
Pollution Control Specialist Sr.|
Minnesota Pollution Control Agency
7678 College Road
Brainerd, MN 56425
|Distributor's Data Set Identifier||Altered Watercourse 6/30/2013 version|
|Distribution Liability||To be determined|
|Ordering Instructions||To be determined|
|Online Linkage||To be determined|
|Section 7||Metadata Reference|
|Contact Person Information||Susanne Maeder,
GIS Project Manager|
Minnesota Geospatial Information Office
658 Cedar Street
St. Paul, Minnesota 55155
|Metadata Standard Name||Minnesota Geographic Metadata Guidelines|
|Metadata Standard Version||1.2|
|Metadata Standard Online Linkage||http://www.lmic.state.mn.us/gc/stds/metadata.htm|