A raster file is a matrix of predefined cells (pixels) with certain number of rows and columns. The level of detail represented by a raster depends on the cell (pixel)…
A raster file is a matrix of predefined cells (pixels) with certain number of rows and columns. The level of detail represented by a raster depends on the cell (pixel)…
Time of concentration (TOC) is an important hydrology parameter which represents the time required for surface runoff to travel from the most hydraulically remote point (normally divide or ridge) in…
This post (3 of 3) is an instruction of combining Land Cover Raster file and HSG Raster file to create a CN raster file for calculating an area-weighted average CN…
Hydrologic Soil Group Data (A, B, C, and D) is an important soil property which impacts the soil infiltration rates and runoff potential. Soils were originally assigned to hydrologic soil…
The SCS (NRCS) Curve Number is used to quantify infiltration loss during runoff calculation. As illustrated in Figure 1, the CN is determined by both soil types (Hydrologic Soil Groups,…
File geodatabase is a collection of files in a folder to store and manage both spatial and nonspatial data. File geodatabase originally came from ESRI ArcGIS and the QGIS has…
QGIS in an open source and free GIS software which can be installed by downloading the installation file at https://www.qgis.org. There are two ways to install QGIS: one is to…
Earth is not a perfect globe and its surface is irregular. GIS needs to use coordinates values (X/Y, or Longitude/Latitude) to describe an actual position/feature on earth in software system.…
RAS Mapper of HEC-RAS Version 6 has some basic but useful GIS functions to complete some GIS operations and spatial analyses common to HEC-RAS modeling, although it could not replace…
The new HEC-HMS published around 2020 has some useful GIS tools to delineate a watershed using terrain data. Unlike HEC-GeoHMS, these standalone GIS commands are an integral part of HEC-HMS…