These maps of rivers around the world were created byEsri UK, a mapping and spatial analytics company, from detailed elevation data collected using remote sensing techniques. The information was taken from Esri’s Living Atlas, one of the world’s largest collections of geographic information.
By eliminating any vegetation or infrastructure, the maps show each river’s geomorphology as it would appear on bare ground. Elevation data can be valuable in highlighting river features and landforms that cannot be seen from normal satellite images, such as slight changes in elevation, run-off, levees, sediment deposits and how the land has changed over time.
One common method in collecting elevation data of this kind is to use a laser scan known as lidar, which measures distance by firing a laser at the ground, most often from a plane, to create a highly detailed picture of the elevation of the earth. Satellite-based sensing is also used for capturing similar data across large areas. This technology is used in various industries including agriculture, conservation, water management and soil science.
The elevation data begins life as a greyscale colour ramp, mapping each elevation value by colour intensity. Using its mapping software, ArcGIS Pro, Esri UK applied different colours to the maps, making historic river paths, small tributaries and other details which cannot easily be seen from satellite images more clearly visible.
Padma River, Bangladesh
The main distributary of the Ganges. The map shows a braided river, with pink used to highlight its main path, showing the lowest elevations – generally equal to sea level. The greens have been used for higher elevations – generally to show land. The darker green shows lower elevations (around five metres above sea level) and fades to the lighter green, which shows higher elevations of around 13 metres (43ft) above sea level. The areas of pink to the right show lower-lying land.
Mississippi, United States
This image reveals the floodplains and pathways that the river has flowed along in the past. It also shows Lake Beulah (an oxbow lake, at the top of the map) and Lake Whittington (another oxbow lake, at the bottom) and the confluence where the Arkansas River meets the Mississippi. The blue colours highlight the path of the river, around 30 metres above sea level, with the deepest blue showing the areas of lowest elevation, and the deepest parts of the river. The greens generally highlight patterns on the land created by historic river paths, fading to a light green which signifies the highest elevation, up to around 60 metres above sea level.
Brahmaputra River, Bangladesh
The darker colours in the braided river shows low elevation, around seven metres above sea level. The deep purple highlights the main path of the river and areas of low-lying land. The lighter colours (orange to yellow, with yellow being the highest) shows higher elevations of up to around 17 metres above sea level.
Amazon, Brazil
This map shows the river delta, where islands of deposited sediment have formed in the middle of the main channel. The darker colours show low elevations, equal to sea level, and the lighter colours show higher elevations, of up to around 38 metres above sea level.
Mackenzie River, Canada
This section of the river is in the process of becoming an oxbow lake. As the sediment builds up, it will become cut off from the main channel. The lighter colours show low elevations, equal to sea level and the darker colours show higher elevations of up to around 11 metres above sea level.
Tien Giang, Vietnam
The lighter colours in the image of this northern branch of the Mekong show low elevations, equal to sea level, and the darker colours show higher elevations of up to around 24 metres above sea level.
Ob River, Russia
The darker colours show low elevations, around 17 metres above sea level, and the lighter colours show higher elevations of up to around 45 metres above sea level.
Rio Negro, Brazil
This shows the braided section of the river before it reaches the Meeting of Waters confluence, close to the city of Manaus, where the dark water of the Rio Negro meets the pale, sandy water of the Amazon. The blues are used to highlight the main river and tributary paths. The deep blue shows low elevations of up to 15 metres above sea level and the lighter blue shows areas of around 35 metres above sea level. The green (around 50 metres above sea level) and yellow (around 65 metres above sea level) highlight tributaries or channels. The oranges and reds highlight higher-lying land up to 115 metres above sea level.