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Add value to your dataset

Elevation datasets are merely providing height above sea level values across an area. However, to truly unlock the potential of your terrain data, it’s essential to uncover the diverse attributes inherent to your landscape. Our suite of derived products extends beyond elevation models, delivering high-quality terrain attributes guaranteed to be a value-add to the product, your order, and your analysis.

Explore some of our most popular derivatives, available as add-ons to your elevation model, below.


This vector layer comprises quality-controlled water features, identified and created during the development of our DEMSA2 products.

The waterbody data product is solely derived from information within Levels 2 and 3 of the DEMSA2 product for the area of interest.

It is important to note that the waterbodies were identified using the same aerial imagery used to create our DEMSA2 product. This means the waterbodies represent the landscape conditions at the time the imagery was captured.

  • Since landscapes can change over time, some water bodies identified in the data may no longer exist, or their characteristics may have changed.
  • Hydrology: It provides a foundation for analysing water resources, including:
    • Surface water mapping: Understanding the extent and distribution of freshwater bodies.
    • Floodplain delineation: Identifying areas at risk of inundation during floods.
    • Water quality modelling: Assessing the health of water bodies and potential pollution risks.
  • Environmental monitoring: It enables tracking changes in water extent over time, potentially indicating climate change or human impacts.
  • Biodiversity studies: Water bodies are vital habitats for various aquatic species, and this data aids in their conservation efforts.
  • Land-use planning: It informs decisions about development projects near water bodies, considering flood risks and ecological concerns.

Height Above Nearest Drainage (HAND)

Height Above Nearest Drainage (HAND) measures the vertical distance between a point and its nearest stream. A HAND map requires a Digital Elevation Model (DEM) and a spatial representation of a region’s river network.

  • Floodplain Delineation:
    HAND is used to delineate floodplains by identifying the areas that are below the elevation of the nearest drainage feature. It helps in mapping areas prone to flooding and assessing flood risk.
  • Flood Inundation Mapping: 
    HAND is used in conjunction with rainfall or river flow data to model and predict the extent of flood inundation. By combining HAND values with other data, such as rainfall intensity or hydraulic models, flood inundation maps can be generated.
  • Hydrological Connectivity: 
    HAND provides information about the connectivity and proximity of each location to the drainage network. It helps in understanding the flow paths and connectivity of water across the landscape, assisting in watershed management and analysis.
  • Terrain Analysis: 
    HAND can be used for general terrain analysis, such as identifying low-lying areas, characterizing topographic features, or assessing slope stability. It provides insights into the relationship between the terrain and the drainage network.
HAND Stellenbosch

Topographical Wetness Index (TWI)

The Topographic Wetness Index (TWI) quantifies a landscape’s moisture conditions based on its topography, combining slope and contributing area data. TWI assesses the tendency of terrain to accumulate or saturation water in a given area:

  • Higher TWI values can indicate areas with greater water accumulation potential
  • Lower TWI values can indicate areas with faster water drainage
  • Hydrological modelling: 
    The TWI is used in hydrological studies to understand and predict the distribution of water flow, stream networks, and watershed delineation.
  • Soil moisture estimation:
    The TWI is correlated with soil moisture content, allowing researchers to estimate soil moisture patterns across a landscape.
  • Ecological studies: 
    The TWI is used to assess habitat suitability for various plant species, wetland delineation, and mapping of hydric soils.
  • Environmental impact assessment:
    The TWI helps in identifying areas prone to runoff, erosion, or potential flooding, aiding in the evaluation of environmental impacts of land-use changes or infrastructure development.

Flow Direction

Flow Direction indicates the direction in which water or fluids would naturally flow across the terrain, driven by gravity from higher to lower elevations. Flow Direction is represented in a raster format, with each cell assigned one of eight directional values, indicating the direction in which water flows out of that cell. This dataset provides crucial information for interpreting flow patterns and drainage pathways.

Flow Dir
  • Watershed delineation:
    Flow direction is used to define the drainage network and determine the boundaries of watersheds or catchment areas. It helps identify the contributing areas that drain into specific points or stream segments.
  • Hydrological modelling:
    Flow direction is an essential input for hydrological models that simulate the movement of water across a landscape. It is used to calculate flow accumulation, stream networks, and flow routing.
  • Flood modelling and analysis:
    Flow direction is used to simulate the movement of water during rainfall events or flood scenarios. It helps identify flow paths, potential flood-prone areas, and flood risk assessment.
  • Erosion and sediment transport:
    Flow direction is relevant for studying erosion patterns, sediment transport, and identifying areas susceptible to soil erosion and sediment deposition.
Flow Direction

Flow Accumulation

Flow Accumulation represents the total sum of water flow from upstream areas to a specific point on the terrain, indicating the total contributing area draining into that point. It is calculated based on the concept that water accumulates as it flows downslope, with smaller streams and tributaries merging to form larger streams and rivers.

  • Cells with a high flow accumulation are areas of concentrated flow and may be used to identify stream channels.
  • Cells with a flow accumulation of 0 are local topographic highs and may be used to identify ridges
  • Watershed delineation: 
    Flow accumulation is used to define the boundaries of watersheds by identifying the areas that contribute flow to specific outlet points or stream segments. It helps in understanding the flow paths and drainage patterns within a watershed.
  • Stream network analysis:
    Flow accumulation is used to identify the main channels, stream orders, and hierarchical organisation of the stream network. It helps in delineating the network’s structure and analysing the connectivity and characteristics of streams.
  • Flood modelling and risk assessment:
    Flow accumulation is utilised in flood modelling to estimate the potential volume of water and the spatial extent of flooding. It aids in identifying areas with high flow accumulation as potential flood-prone areas.
  • Ecosystem and habitat analysis: 
    Flow accumulation can provide insights into the availability of water resources and its influence on vegetation distribution, wetland delineation, and ecological habitat suitability
Flow Accumulation

Flow Network

A Flow Network is created by analysing terrain features and hydrological processes based on a DEM. It involves calculations of flow direction, flow accumulation, and extraction of stream networks. These parameters delineate water flow pathways, constructing a network representation of the drainage system.

This network provides valuable insights into the connectivity between different areas through water movement, and how water flows are organised throughout the landscape.

  • Watershed Delineation: 
    The flow network helps in delineating watersheds or drainage basins. Watersheds are delineated by identifying the contributing areas that drain into specific outlets or stream segments. This information is crucial for understanding the movement of water and the boundaries of catchment areas.
  • Hydrological Connectivity: 
    The flow network reveals the connectivity of streams and channels in the landscape. It helps in understanding the spatial organization of the drainage system, identifying tributaries, and assessing the connectivity of water flow across the terrain.
  • River and Stream Management: 
    The flow network assists in managing river systems and stream networks. It provides information about the structure and organization of streams, aiding in the identification of key river segments, stream orders, and channel networks.
  • Water Resource Planning: 
    The flow network is essential for water resource planning, including flood risk assessment, water supply management, and ecological studies. It helps in understanding the movement of water, assessing the impact of land use changes on water flow, and identifying areas prone to flooding or erosion.
Flow Network

Sink Filled DEM & Closed Depressions

Sinks, with undefined flow directions due to errors in elevation data, are assigned values representing the sum of their potential directions. They often occur in low-lying areas without outlets, contributing to closed depressions where water accumulates.

Sinks arise from errors in elevation data or natural features like craters. In a standard DEM, water flow calculations would stall at these points. Filling a DEM involves raising the elevation in sinks to create a continuous downhill flow path throughout the model. Sink filling allows for accurate hydrological analysis like flow accumulation and stream network generation.

  • Hydrology: They enable accurate modelling of water flow, including:
    • Floodplain mapping: Identifying areas at risk of flooding during heavy precipitation.
    • Watershed analysis: Studying water movement through a drainage basin.
    • Soil erosion prediction: Assessing areas susceptible to soil erosion by water runoff.
  • Environmental studies: They aid in understanding the distribution of water resources and potential impacts on ecosystems.
  • Infrastructure planning: They help in designing drainage systems, dams, and irrigation projects.

Closed depressions are formed by surrounding higher terrain, restricting water flow and leading to the accumulation of water, creating ponds, lakes, or wetlands. These features, commonly found in karst landscapes, impact local hydrology, ecology, and land use.

  • Hydrology: They represent areas of potential water storage and influence local drainage patterns.
  • Ecology: They provide critical habitat for wetland-dependent plants and animals.
  • Land-use planning: Identifying closed depressions helps in managing water resources and avoiding development in flood-prone areas.
  • Climate change studies: Monitoring closed depressions can reveal changes in precipitation patterns and groundwater levels.
Sink filled DEM & Closed depressions

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