Flow Direction
In hydrological analysis, the direction water will flow out of each cell in a raster DEM, foundational for watershed and stream network modelling (standard GIS usage).
What is meant by Flow Direction?
In GIS and hydrology, "flow direction" describes the course that water follows as it traverses the terrain's surface. A raster dataset is typically used to depict it, with each cell indicating the direction of water flow from that cell to one of its neighbouring cells based on the steepest downhill slope. When examining the movement of water across a landscape, determining the direction of flow is an essential step that aids in modelling watershed boundaries, stream networks, and drainage patterns. GIS tools can predict areas of accumulation, simulate water runoff, and assist in flood risk assessment by giving each cell in a digital elevation model (DEM) a flow direction. Standard techniques, such as the D8 algorithm, which takes into account eight potential directions for water to flow from each cell—north, northeast, east, southeast, south, southwest, west, and northwest—are usually used to encode flow direction. Numerous hydrological analyses and environmental management applications are made possible by this core data.
Related Keywords
In GIS, flow direction indicates which way water exits each raster cell, usually indicating the neighbour that is the steepest downhill. It is employed to understand the flow of water across a landscape and to model drainage patterns.
The route that water follows as it travels across the surface of the earth or through the subsurface, usually propelled by gravity, is referred to as the hydrological flow direction. It shapes drainage patterns and has an impact on watershed management by determining how rainfall, rivers, and groundwater move from higher to lower altitudes. Predicting floods, controlling soil erosion, and efficiently allocating water resources all depend on an understanding of flow direction.
A crucial procedure in hydrology and GIS for figuring out how water moves across a terrain is flow direction analysis. It determines the direction of water movement from each cell to its steepest downslope neighbour by examining digital elevation models (DEMs). Planning water resource management and land-use policies, forecasting flood routes, modelling watershed drainage patterns, and preventing soil erosion all depend on this data.
Using the D8 approach for hydrological study, DEM flow direction assigns a downslope direction to each cell depending on elevation, illustrating the route water would take across terrain.