Hydrology
Weighted Curve Numbers, with basins and Tc worked out from terrain.
CN Studio computes a weighted SCS Curve Number from your boundary, USDA soils and land cover. It can also delineate the subbasins for you, from NHDPlus catchments, LiDAR or USGS 3DEP terrain, your own DEM, or USGS StreamStats pour points, and derive a TR-55 time of concentration from the terrain. No GIS desktop required.
CN Studio
Monthly subscription
How it works
- Upload a drainage or project-area boundary, or drop pour points.
- Pick the land-cover source and delineation mode.
- Download CN results, maps and the Tc report.
What goes in, what comes out
You provide
- Drainage boundary OR Project area boundary .shp + .shx + .dbf + .prj or .dxf (legacy only)
Legacy mode: drainage polygons. Auto-delineate modes: a single project-area boundary (.shp only — no DXF). Mismatched-CRS shapefiles auto-reproject; logged, not errored. - DEM GeoTIFF (Custom Terrain delineation OR Tc-from-terrain) .tif / .tiff
Required for Custom Terrain delineation and Tc-from-terrain. Must be a projected CRS (UTM, state plane, Albers); geographic lat/lon DEMs are rejected. - Min Subbasin Area (terrain delineation modes only) number (acres)
Subbasins below this are merged into their largest neighbor. Default 0.5 ac. Set 0 to disable. Ignored by NHDPlus and legacy modes. - Land-use layers (Custom Shapefile land-use mode only) .shp + .shx + .dbf + .prj
One shapefile per land-use category. Filename (without extension) must match the Custom Shapefile reference table; unrecognized filenames are skipped with a log warning. - NLCD year (NLCD mode only) dropdown
Vintage to fetch from MRLC: 2001, 2004, 2006, 2008, 2011, 2013, 2016, 2019, 2021. CONUS only. - State + County (soils) dropdowns
USDA SSURGO source. Auto-delineate modes auto-resolve every county the AOI touches and merge with your selections. - EPSG code number
Projected US-Feet CRS for area math (auto-detected when possible). - Time of Concentration per polygon (TR-55 + Manual Tc only) number (hours)
Per-polygon dialog that opens after CN finishes; area + weighted CN shown for identification. Values 0-24 hours. Skipped under 'Compute from terrain' or auto-delineate terrain modes.
You get
- CN_Results shapefile set .shp
Per-polygon results: per-HSG × per-LU acreage columns (e.g. A_IMPV, B_NLCD_21), Total_Acre, W_CN. TR-55 adds Tc_hr / Rain_Type / TR55_Q1 … TR55_Q100; terrain Tc adds Tc_sheet / Tc_shal / Tc_chan / LFP_ft; USGS Regression adds USGS_Reg / DAmi / Imp / Q2 … Q500 / Env. Auto-delineate modes consolidate to one row per basin DN. - Tc Report — Tc_Report.pdf (terrain Tc only) .pdf
Sits in the ZIP root next to CN_Results.shp and landcover_report.pdf. One page per basin: header (id, area, P2, total Tc) and per-segment inputs (sheet n + L + slope + elevations + LU; shallow surface + L + slope + v; channel V/T/R/N + z + b + depth + R + n + slope + v). Plan-view + longitudinal-profile figures per page; summary table on page 1; footer carries the methodology version. - Composite report map — landcover_report.pdf .pdf
Vector PDF map with color-keyed land cover, drainage overlay, centroid-labeled polygon IDs, scale bar, and north arrow. Tables underneath: LU × HSG breakdown with per-polygon subtotals + gold area-weighted GRAND TOTAL; USGS Q table (if USGS on); TR-55 Q table (if TR-55 on). - Shapefiles — shape/ (every shapefile except CN_Results) .shp
Every vector layer the run produced, except the primary CN_Results.shp which sits at the ZIP root. NHDPlus mode: subbasins.shp + streams.shp (NHD network clipped to the AOI). StreamStats mode: subbasins.shp (one row per pour point with USGS Q-stats) + project_area.shp (union watershed). Terrain / Custom Terrain modes additionally drop watershed.shp, subbasins_full.shp (raw, pre-classification), longest_flow_path.shp and pour_point.shp into this folder. Single drop-into-GIS destination — no folder hunting. - Terrain rasters — terrain/ (terrain modes only) .tif
DEM-domain GeoTIFFs the terrain pipeline produces: dem_clip.tif, facc.tif, d8_pointer.tif, streams.tif, watershed.tif, subbasins.tif, strahler.tif. dem_mosaic.tif appears when more than one source tile was stitched. Vector outputs that used to share this folder now live under shape/. - Process log — process_log.txt .txt
Step-by-step job log: SSURGO/VGIN cache hits, NLCD acreages, DEM fetch + coverage, hydrology progress, Tc per-basin XS results, NOAA Atlas 14 lookups, USGS calibration advisories. First place to look on warnings or failures.