USGS National Elevation Dataset (NED) - Digital Elevation Models (DEM): The original version of this dataset was downloaded from the USGS EROS Data Center ftp site at <ftp://edc.usgs.gov/pub/data/ned/>. The original NED data may not be available using this site and is distributed on the Seamless Data Distribution System site (<http://seamless.usgs.gov/viewer.htm>). The NED tiles that comprise the extent of the state of Michigan were downloaded and converted to integer grids in decimeters to save disk space. The grids were seamed together using the MERGE command in Arc/Info. The statewide mosaic was projected to Michigan GeoRef and clipped to the Michigan Geographic Framework Version 3b county boundaries with a one mile buffer applied.
County boundaries(Michigan framework version 3b), Lake and River polygons (Michigan Framework version 1b), and Rivers and Drains (Michigan MIRIS): These datasets were obtained from the Michigan Center for Geographic Information (<http://www.michigan.gov/cgi>). Two buffer shapefiles were created by buffering each county boundary by 90 meters and 1 mile using ArcGIS version 8.3. Legacy datasets such as version 1b Framework and original MIRIS hydrography layers were used since inconsistent updates have been made to these layers since their creation. The files listed above have all been processed in a similar fashion. An exception is the lakepoly shapefile, which had lakes greater than or equal to 5 acres queried out for processing. Additionally, all lakes that were obvious sewage treatment settling ponds were removed from the dataset (these have distinct geometric shapes and represent perched water). County datasets for each layer were combined into statewide datasets and county boundaries with a 1-mile buffer were used to clip out each county file. The clipped county shapefiles were converted into 30-meter raster grids. The resulting county grids were reclassified to give feature areas a value of 1 and all others areas a NoData value. Next, all grids were run through a raster calculator against the USGS NED Digital Elevation Model (DEM) to obtain an elevation value for each feature related cell (grid * DEM). Only the MIRIS drain layer was treated differently with 2 feet subtracted to set each drains cell values (grid * DEM - 2). The resulting point files, for each feature dataset, contain an elevation attribute value for each point (minus 2 feet for drains).
Unconfined Drift Wells (MDEQ Wellogic Database): Antrim, Crawford, Kalkaska and Otsego counties have very little surface hydrography and therefore needed to be supplemented with unconfined drift well data. The water well data used was derived from the State Wellogic Database. The wells for Antrim, Crawford, Kalkaska and Otsego counties are queried from the Wellogic database, then queried for drift wells that have little or no confining material between the static water elevation and the well screen. These counties are dominated by sandy soils, so the static represents the first water most of the time. The elevation values were determined by subtracting the static water level from the surface elevation determined from the 30 meter DEM. The location of the wells is approximate which occasionally results in an incorrect surface elevation being derived, resulting in an erroneous static. Therefore the wells data was inspected and wells with significantly different static water levels, compared to nearby features, were removed.
Soils and Wetlands
For the purpose of this project, SSURGO version 2 digital soils were determined to be the most desirable soils dataset. However, SSURGO version 2 soils were not available for every county at the time of processing. In the absence of SSURGO 2 data, this project utilized, in order of preference, SSURGO version 1 digital soils data, MIRIS unrectified digital soils data or National Wetlands Inventory (NWI) data.
The following list indicates the primary dataset for each county at the time of processing.
SSURGO version 1 digital soils: Alcona, Antrim, Barry, Bay, Branch, Clinton, Crawford, Emmet, Gladwin, Hillsdale, Iosco, Marquette, Midland, Montmorency, Presque Isle, Saginaw, Tuscola. SSURGO version 2 digital soils: Alpena, Arenac, Baraga, Berrien, Charlevoix, Cheboygan, Chippewa, Genesee, Grand Traverse, Gratiot, Isabella, Kalkaska, Keweenaw, Lapeer, Leelanau, Luce, Mackinac, Macomb, Mason, Mecosta, Monroe, Montcalm, Muskegon, Newaygo, Oakland, Oceana, Ogemaw, Osceola, Oscoda, Otsego, Roscommon, Sanilac, Shiawassee, St. Clair, St. Joseph, Wayne. MIRIS digital soils: Ingham, Jackson, Kent, Lenawee, Livingston, Washtenaw. National Wetland Inventory wetlands: Alger, Allegan, Benzie, Calhoun, Cass, Clare, Delta, Dickinson, Eaton, Gogebic, Houghton, Huron, Ionia, Iron, Kalamazoo, Lake, Manistee, Menominee, Missaukee, Ontonagon, Ottawa, Schoolcraft, Van Buren, Wexford.
National Wetland Inventory (NWI) Wetlands (Michigan Department of Natural Resources): Merged all county Wetland shapefiles into one statewide, although incomplete, shapefile. Queried Wetlands shapefile for all palustrine wetlands > or = 1 acre and saved results as a new shapefile. For NWI counties and counties that border those counties using NWI data, clipped merged and edited wetland shapefile with each county's 1-mile county buffer shapefile. For each relevant county, created a 90 meter grid from the wetlands shapefile (shapegrid command in ArcInfo workstation). Reclassified the grid to set wetlands cells to a value of 1 and all other cells to a value of NoDATA. Multiplied the wetlands grid by the co-located Digital Elevation Model (DEM) and subtracted 1 foot to set each wetlands cell value (grid * DEM - 1). The resulting value becomes the elevation value represented by the corresponding cell in the DEM minus 1 foot. Created a point coverage from the 30 meter wetlands grid (gridpoint command in ArcInfo workstation). The resulting point file contains an elevation attribute value for each point.
Michigan MIRIS Soils (unrectified digital soils): Obtained MIRIS soils datasets from the Michigan Center for Geographic Information (<http://www.michigan.gov/cgi>). This dataset is the result of digitizing polygons from County soil surveys, registering polygons and merging into county files. Merged all MIRIS soils shapefiles into one statewide, although incomplete, shapefile. Queried MIRIS soils for all soil polygons > or = 1 acre and saved results as a new shapefile. For MIRIS soils counties and counties that border those counties using MIRIS soils data, clipped merged and edited MIRIS soils shapefile with each county's 1-mile county buffer shapefile. For each relevant county, created a 90 meter grid from the MIRIS soils shapefile (shapegrid command in ArcInfo workstation) and set the resulting grid value to the value represented by the WTDEPH attribute value in the shapefile. Subtracted the MIRIS soils grid from the DEM (DEM - grid) to set each grids cell value. The resulting value is the elevation value represented by the corresponding cell in the DEM minus the WTDEPH value in the original shapefile. Created a point coverage from the 90 meter MIRIS soils grid (gridpoint command in ArcInfo workstation). The resulting point file will contain an elevation attribute value for each point.
NRCS SSURGO Soils - Version 1 (rectified digital soils): Downloaded SSURGO version 1 digital soils from either the NRCS SSURGO database (<http://www.ncgc.nrcs.usda.gov/products/datasets/ssurgo/>) or from the NRCS soil data mart (<http://soildatamart.nrcs.usda.gov/>). Merged all SSURGO 1 county soils datasets into one statewide set. Queried merged SSURGO 1 soils dataset for WTKIND = APPARENT and Acres greater than or equal to 1 acre. The statewide dataset was then clipped using each county's 1 mile buffer shapefile. A 90 meter grid was then created for each relevant county, with the grid value set to the WTDEPH attribute value in the shapefile. The resulting grid was then subtracted from the co-located DEM to set the final cell values. Finally, a point file was created from the 90 meter grid. The resulting point file contained an elevation value for each point.
NRCS SSURGO Soils - Version 2 (rectified digital soils): Download SSURGO version2 digital soils from either the NRCS SSURGO database (<http://www.ncgc.nrcs.usda.gov/products/datasets/ssurgo/>) or from the NRCS soil data mart (<http://soildatamart.nrcs.usda.gov/>). The MS access table for each SSURGO dataset was queried for soils with the water table in the sampled soil zone (6 to 7 feet, depending on when the survey was done). Additionally, the soils dataset was queried for wet soils, water in root zone for at least one month and area greater than or equal to 1 acre. Each queried SSURGO 2 dataset was merged to create a statewide dataset. The dataset was then clipped using each county's 1 mile buffer shapefile. A 90 meter grid was then created for each relevant county, with the grid value set to the Depth_H_Feet value in the shapefile. The resulting grid was then subtracted from the co-located DEM to set the final cell values. Finally, a point file was created from the 90 meter grid. The resulting point file contained an elevation attribute value for each point.
Great Lakes Shoreline: Downloaded shoreline shapefiles from the Michigan Center for Geographic Information (<http://www.michigan.gov/cgi>). Merged all shoreline shapefiles into one statewide shapefile. Buffered shoreline shapefile by 90 meters. Created a 30 meter grid (shapegrid command in ArcInfo workstation) from the statewide shoreline shapefile. Created a point coverage from the grid (gridpoint command in ArcInfo workstation). From the point coverage, selected all points that fall on the lake side of county boundary and exported selection to new shoreline shapefile. Selected shoreline points and set elevation values based on the mean monthly lake levels for the period from 1918 to 2002 as defined by the International Great Lakes Datum of 1985 (IGLD85). Values for individual lakes and Rivers are specified in the following list.
Lake Superior: 602 feet Lake Michigan: 579 feet Lake Huron: 579 feet Lake Erie: 571 feet Lake St. Clair: 574 St. Marys River (Lake Superior to Sugar Island): Linear interpolation using 1:24,000 USGS topographic quadrangles as reference. St. Marys River (Sugar Island to Munuscong Lake): Linear Interpolation using 1:24,000 USGS topographic quadrangles as a reference. St. Clair River: Linear interpolation between Lake St. Clair and Lake Huron Detroit River: Linear interpolation between Lake St. Clair and Lake Erie
Interpolation Attribute - Elevation, Method - Kriging, Handling of Coincident Samples - Use Maximum, Transformation - None, Order of Trend Removal - None, Semi-variogram Model - Spherical, Lag Size - 300 (horizontal coordinates are in meters), Number of Lags - 12, Search Direction - None, Searching Method - Neighborhood, Neighbors to include - 12, Minimum Neighbors to Include - 6, Shape Type - 4 sectors with 45 degree offset, Cell Size of Output - 30 meters
Using ArcGIS Spatial Analyst, clipped each interpolated first water grid using 90 meter buffered county boundary shapefiles. Set output resolution to 30 meters.