Modelling sedimentation loads in the upper river basin using Revised Morgan Morgan Finney Model

Sedimentation is a natural process whereby eroded soil particles are transported by water and deposited in riverbeds. In the Upper Athi River Basin, this process has been accelerated by anthropogenic activities such as intensive agriculture, industrialization, and population growth, coupled with biophysical factors including climate variability and soil type differences.

The basin stretches from humid tropical rainforest zones upstream to fragile arid and semi-arid savanna areas downstream, influencing the rate of erosion and sediment transport.

Problem Statement

The problem addressed is the increasing sediment yield, which threatens water resources, agricultural productivity, and ecosystem stability. The study aimed to predict sedimentation loads within the basin and assess the influence of land use, climate, and soil conservation measures.

Methodology

To achieve this, the Revised Morgan Morgan Finney (RMMF) model was integrated with Cellular Automata Markov Chain (CA–Markov) analysis. Datasets incorporated included:

• Digital Elevation Models (DEM)

• Soil Data

• Climate Data

• Land Use/Land Cover (LULC)

The models simulated processes such as surface runoff and soil detachment by raindrops, capturing erosion and sedimentation dynamics.

Results

Results revealed annual sediment loads of:

• 2003: 10.6 million tons (15.15% increase)

• 2013: 22.6 million tons (32.15% increase)

• 2023: 36.9 million tons (52.69% increase)

These findings highlight the urgent need for sustainable land and water management to support Vision 2030 goals.

Figure 1: Landuse Landcover maps for the year 2003, 2013 and 2023

Figure 2: Annual rate of soil particle detached by raindrop

Figure 3: Sediment yield maps

Prepared by Elizabeth Muraya, Geospatial and remote sensing expert