A bathymetric map shows the shape and depth of a lake. A hypsographic curve takes that information one step further by showing how the lake’s surface area and water volume change with depth.
This relationship matters because lake-management decisions rarely depend on maximum depth or total acreage alone. Aquatic herbicide calculations may depend on the volume of water within a treatment area. Aeration-system design requires an understanding of basin shape, depth distribution, and water volume. Storage and flood-planning discussions depend on how much additional water the basin can hold as its level changes.
BioBase automatically converts mapped bathymetry into a hypsographic analysis that helps managers examine these relationships without performing separate manual volume calculations.
BioBase’s primary strength is its power as an automated processing engine delivering high quality geospatial data layers on aquatic habitats with very little user input outside of the physical effort to drive a boat and passively log sonar over an area of interest. In addition to the online analysis tools within BioBase like the polygon tool and automated statistical reports, users can export raw depth, vegetation, and bottom hardness data along their track, in X,Y,Z grid format, Google Earth imagery, Lowrance or Simrad Charts, AND NOW ESRI SHAPEFILES OF DEPTH CONTOURS! This feature has been in high demand for survey companies and governments who require detailed water volume analysis for aquatic habitat and fisheries management. Below we walk you through some helpful tips about the feature and how to use it.
Go To Tools – Export Options and click “Export Shapefiles”
D_Areas are polygon areas of each contour interval. D_Contours are contour polylines. NOTE: shapefile exports’ coordinate system is WGS 1984 (CRS 4326).
Example from a small lake:
589.3 acre (2,384,812.5 sq. m) lake as viewed in BioBase.Depth Areas as polygons are bundled into the zipped export. This will allow the user to carry out detailed water volume analysis as a function of depth with fewer post-processing steps than were originally required when data was only exportable as points. The MAX_ELEV field in the Attribute table is the contour value in meters and MIN_ELEV is the outer range or deeper contour value of the Depth Area polygon.
The D_Areas shapefile contains many overlapping, redundant polygon features that need to be deleted. To determine which rows to delete, calculate the difference between the max and min elevation values and only keep the rows with a difference of 1 foot (0.3048 meters).
For a complete video tutorial on working with D_Areas shapefiles please visit our YouTube channel.
Exported 1ft contours. The user can control whether contours are displayed in imperial or metric In BioBase, but the values are always stored in metric (e.g., for the 1ft contour, the VALUE field in the attribute table will show 0.3048). For metric contours, they come out in 0.25m intervals.
Shapefiles for vegetation and bottom hardness layers are also available for export as BioBase continues its mission to deliver water and fisheries resource professionals high value data products in the hopes that you can focus less of your efforts on making maps and more on the important tasks of research and conservation.
