Granulometric and geomorphological characteristics of Rezu Khal canal, Bangladesh: Inferences for sustainable ecosystem and management

Abstract

The geomorphology and sedimentological characteristics can build the sustainable ecosystem according to the existing environment. The present study concentrates on the findings of the total network of RezuKhal at the Cox's Bazar district that includes data on geomorphologic features and sediment characteristics. We used Geographical Information System (GIS) as a suitable method which depicts the process of data collection, data management, preparation, and map representation using ArcGIS software. The total catchment area of RezuKhal is estimated as 140 sq.km in Bangladesh. The data includes geomorphologic parameters and sediment obtained from samples collected in three sites (A, B, and C) in the catchment area of Rezu Khal. The sampling was performed in each station in every month of the hydrological year 2013. The key map indicates that one of the major rivers drains from Myanmar, 3 tributaries from Ukhia Upazilla and the other two originate from Ramu Upazila. These rivers were identified crisscrossed on the long plain land. The total length of the main river was 43.46 sq.km and the length of major tributaries 65.41 sq.km, while the total length of major sub-tributaries are 40.69 sq. km. The analysis of the sedimentation of the Rezu Khal area demonstrated that it is dominated by fine sand and very fine sand in the main river and the different tributaries. Morphologically, the study domain can set on the three sites, including, Site A (estuarine part), Site B (long plain land area) and Site C (bottom of the hilly area). The sedimentological part in this study included concentration of sediment temperature (S-temp, 24–33°C), SOC 0.29% and 4.485%, (SOM) fluctuated between 0.51% and 7.73%. The average sediment texture properties values are 49.57 ± 0.01, 25.38 ± 0.01, 11.55 ± 0.02 Furthermore, it has been grouped as medium sand, medium silt, and field water capacity, which varied significantly in different seasons and sites (p < 0.05). The substantial variation was found in temperature, coarse silt, and sediment pH in terms of sites (p < 0.01), while PO4-P change with seasons (p < 0.05). Organic matter, organic carbon, and nutrients were gathered in the mouth of the estuary and formed a unique sand dune habitat which provided food and nutrients for benthic aquatic fauna. The sediment characteristics were significantly affected by its seasonal variation and human activities of Rezu Khal. The tributaries and its sub-tributaries of Rezu Khal have different applications with their unique environment, such as agriculture, irrigation, pisciculture, drinking and sand collection, etc. The qualitative and quantitative findings of the present study can estimate the existing resources of the Rezu Khal.