Why do urban area's have flashy hydro-graphs?

Urban areas often have flashy hydrographs due to increased surface runoff caused by impervious surfaces like pavement and buildings, which prevent water from infiltrating into the ground. This leads to faster and higher peak flows during storms, resulting in rapid rises and falls in streamflow. Additionally, the presence of stormwater drainage systems can further exacerbate flashy hydrographs by quickly conveying runoff to streams.