when a rock has been weakened and broken up by weathering. Weathering is the breaking down of rocks, soils, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms. Weathering and erosion help shape Earth's surface.
( erosion is different from weathering and weathering is the answer you are looking for! I hope this helped. I looked into different areas to find more information about weathering)
Because of Dhaka's position below sea level the city experiences yearly flooding, particularly around the monsoon seasons and has the constant threat of rising sea levels, which would of course cause more flooding.