When are へ and に used together?

Question

おばあさん は 川（かわ） へ せんたく に でかけます。

Why is there both へ and に? When can they be used together? Can someone break down the sentence for me to understand?

Answer 1

As far as I know it's fine to use に after both verb stems and nouns when given as reasons for something.

E.g. お土産に買う - I will buy it as a souvenir

And to give a more concrete answer to your question: The particles convey different information, one is direction and the other is reason. Of course you can't have two directions, but that is not the case here.

Answer 2

The に you presented indicates purpose of going rather than a direction.

Related: Is it true that only movement verbs can take [V-stem]に to express a purpose?

Constituent parts:

• おばあさんは(The woman(topic))　

• 川へ(in the direction of river)　

• せんたくしに(for the purpose of laundry)　

• でかけます(go out)

Sentence: The woman goes out to the river to do laundry.