Ducks and geese are very common in urban and suburban lakes, streams, and ponds. Waterfowl cause pollution when they spend time in stormwater ponds and excrete directly into and around the water. Stormwater ponds are typically designed to enhance water quality, but they are not capable of treatment at this level. The duck waste decreases the natural filtration benefit that detention ponds are supposed to create.
When waterfowl congregate in ponds, the fecal levels skyrocket. Ducks are commonly seen in large groups and and overwhelm any water quality system. Preventing ducks in stormwater ponds at the city-level seems daunting, but reducing impacts in each neighborhood is crucial. "Shooing" ducks away from stormwater ponds is good for the pond and the surrounding waters.
The best way to prevent ducks in your neighborhood is to never feed the ducks. Ducks will always come back if they think they will get an easy meal and they will not forget who fed them. Bread and other foods commonly fed to urban ducks is actually unhealthy for the animals and are not part of their natural diet.