along the streets/banks

[joham]

1. They built a house on the banks of the Severn River.
2. So while walking down the streets of Oakland with Shimon, I found myself on guard, waiting for some brother to give me flack about being with a White boy.
3. He took them for a stroll along the banks of the stream.

Why is the plural used with the nouns 'street' and 'bank' in these sentences? Wouldn't the singular form of 'bank' and 'street' be more reasonable?
Thank you in advance.

[Soup]

Hello joham

1. They built a house on the banks of the Severn River.

• It probably means portions of the same bank.

2. So while walking down the streets of Oakland with Shimon, ... .

• They walked down more than one street.

3. He took them for a stroll along the banks of the stream.

• See 1. It could also mean they walked on both sides, e.g., first the left-side, then crossed by bridge, then the right-side.