When it rains, water travels directly over these impermeable surfaces, into pipes and directly into the creek. Less water is absorbed into the ground. As a result, more water arrives in the creek channel far more quickly after it rains. Urbanization therefore tends to speed run-off and produce higher peak flows. The effect is shown in the graph below.
Urbanization can also reduce summer low flows as less water is stored in the surrounding soil.
A staff gauge for measuring stream flow has been installed on Bowker Creek near Trent Street. It is hoped a stream flow monitoring program will be developed in the near future. As water travels across urban surfaces, it dissolves and carry pollutants into the creek channel. Oils, detergents, fertilizers, animal feces, other pollutants and sediment are deposited in the urban watershed. Just add water, and you have a toxic soup that ends up in the creek channel and eventually the ocean.