Geomorphology assessment of watershed
Geomorphology assessment of the watershed is a hydrology approach for studying the physical properties of a river basin or watershed. It entails measuring and analyzing several morphological factors in order to comprehend the system's hydrological behavior. Some of the most popular morphometric parameters used in hydrological investigations are:
1. Drainage area: The total land area that contributes runoff to a certain point in a river network. It is commonly expressed in square kilometres or square miles.
2. Stream length: The total length of all streams within a watershed, including major channels and tributaries.
3. Stream order: Based on where they are located within a river network, streams are sorted into several orders. Since first-order streams are the smallest, higher-order streams are created when they combine.
4. Stream density: It is determined by dividing the drainage area of a watershed by the sum of the lengths of all of its streams. The quantity of streams indicates how well-developed the drainage system is.
5. Drainage density: Drainage density, like stream density, is the sum of all stream lengths divided by the drainage basin's surface area.
6. Basin shape parameters: These variables characterize the size, shape, and form of a watershed and include the elongation ratio, circularity ratio, compactness coefficient, etc.
7. Relief ratio: It is determined by multiplying the horizontal distance of a watershed by the elevation difference between its highest and lowest points.
8. Slope steepness: This parameter indicates how steep or gentle the terrain is within a watershed and can be measured using digital elevation models (DEMs).
9. Hypsometric curve: It depicts the area-elevation connection within a watershed and offers details about its topographic features.
10. Strahler stream order: This categorization system assigns numerical values to various stream segments based on their hierarchical positions within a river network
Hydrologists can get insights about a watershed's hydrological behavior, such as runoff potential, flood vulnerability, erosion potential, and overall drainage characteristics, by analysing these morphometric parameters. This data is critical for a variety of applications such as water resource management, flood predictions, and environmental planning.
The measurement and quantitative analysis of the Earth's surface structure, including its shape, elevation, slope, and dimensions of its landforms, is known as morphometric analysis. The hydrologic response of a basin is largely governed by morphometric variables, which also serve as markers of the process of landform formation. Basin morphometry has been used to forecast or explain geomorphic processes, such as forecasting the heights of floods, evaluating sediment output, and calculating erosion rates
Previous studies in this field have had a wide range of objectives, with some focusing on the geomorphology of watersheds, others on the combined use of morphometric parameters and field data for hydrologic modelling, and yet others on the use of morphometry, geology, and land-use information to assess flood hazard. Our studies investigated 14 sub-basins in Wadi Nisah calculated to assess the flash flood hazard using GIS software, TOPAZ module in WMS software. The stream network decreases from high to low elevation due to decreased density. Sub-basins have circular shapes, while those with elongated shapes have steeper descents.
GIS analysis identifies sub-basins in Wadi Nisah that are at risk of flooding. High susceptibility sub-basins are categorized as high, moderated, and high, while moderate and low susceptibility sub-basins are classified as intermediate. The morphometric ranking method ranks sub-basins based on their overall score values, with low flooding susceptibility being represented by 55.6% of the total area. Moderate flooding susceptibility is represented by 4.8% of the total area, while high susceptibility is represented by 39.6%.