Morphometric Properties and Land Cover Dynamics of River Shemankar Upper Drainage Basin, Plateau State, Nigeria

The Blueprint of a River's Neighborhood

Imagine a river basin not just as a collection of water flowing downhill, but as a bustling, living neighborhood. In this neighborhood, the rivers are the streets, the hills are the buildings, and the soil is the pavement. Scientists who study these places are called geomorphologists and hydrologists. They use a special tool called morphometric analysis, which is essentially a way of measuring the "body shape" of a river system. Just as a doctor might measure your height, arm span, and weight to understand your health, these scientists measure the length of streams, the number of branches, and the steepness of the land to understand how water moves, where it might flood, and how much rain soaks into the ground.

Another crucial part of this story is land cover, which is simply what is sitting on top of the ground. Is it a lush green forest, a rocky mountain, a busy city, or a farm? Think of land cover as the neighborhood's "outfit." When the outfit changes—say, from a soft, spongey forest to a hard, impermeable city street—the way the neighborhood handles rain changes completely. This matters to everyone because if we don't understand how these neighborhoods are shaped and how they are changing, we can't predict floods, manage water for farming, or protect our homes from erosion.

The Story of River Shemankar's Changing Face

In this study, a team of researchers decided to take a close-up look at the "neighborhood" of the River Shemankar Upper Drainage Basin in Plateau State, Nigeria. They wanted to map out its physical shape and see how its "outfit" had changed over time. To do this, they acted like digital detectives, using satellite images and computer models of the earth's surface (called DEMs) to measure the basin's bones and skin.

First, they measured the basin's "body." They found it to be a massive area of 4,249.5 km², roughly the size of a small country. It is a 6th-order basin, which means it has a complex hierarchy of streams, starting with tiny trickles (1st order) that merge into larger rivers, eventually forming one giant main river (6th order). The basin is quite tall, with a total height difference (relief) of 1,380 meters from its highest peaks to its lowest valleys. However, despite being tall, the "streets" (streams) are actually quite sparse. The drainage density is low at 0.79 km/km², meaning there aren't many streams packed tightly together. This suggests the ground is good at soaking up water, and the basin is shaped like a long, stretched-out oval rather than a perfect circle.

Next, the team looked at how the neighborhood's "outfit" changed between the years 2000 and 2024. The results showed a dramatic makeover. In 2000, the area was a mix of farms (51.3%) and rocky outcrops (28.5%). Fast forward to 2024, and the landscape had transformed. Agricultural land exploded, taking over 80.8% of the basin. Meanwhile, the rocky outcrops and natural vegetation shrank significantly. The built-up areas (cities and towns) also grew, tripling from a tiny 0.5% to 3.7%. It's as if the neighborhood swapped its green, rocky coat for a heavy, uniform farming jacket.

The researchers then asked: "Does this new outfit change how the river's body works?" They ran statistical tests to see if the amount of farming or rocks was linked to how many streams existed. The answer was a loud "yes." They found a strong positive relationship (with a statistical score, R², between 0.70 and 0.81) between agricultural land/rocky outcrops and the number of streams. In plain English, the more the land was cleared for farming or exposed as rock, the more new little streams and channels formed. This happens because bare soil and rock don't soak up water well, so the rain runs off quickly, carving new paths. Conversely, vegetation had a weak, inverse effect; where plants remained, fewer new streams formed because the plants acted like sponges, holding the water and stopping it from carving new channels.

Finally, the team had a side quest to see if their digital tools were telling the truth. They compared two different types of satellite maps: one from the ASTER sensor and one from SRTM. They wondered if one tool gave a better picture of the river's shape than the other. They ran a statistical test called ANOVA, which checks if two groups of numbers are significantly different. The result was surprising: there was no significant difference (p = 0.285) between the two maps. Both tools gave very similar measurements of the basin's shape. However, the SRTM map seemed to catch a few more tiny streams and showed slightly higher numbers for how "intense" the drainage was, making it a slightly sharper tool for seeing the fine details of the water flow.

In the end, the study reveals that the River Shemankar basin is a stable, well-organized system that is currently being reshaped by human hands. The rapid expansion of farming and the loss of natural vegetation are actively changing the river's structure, creating more channels and altering how water moves. While the digital maps used to study this are reliable, the message is clear: the way we dress our land matters. As the "outfit" shifts from nature to agriculture, the river's body is responding, carving new paths and changing the flow of life in the basin.