You can't forbid it if you can't enforce it
Leviticus 18 lists all the forbidden sexual relations with women who are under the protection or possession of another man. These are all the situations in which another man would have cause for dispute. It forbids sexual relations with the daughters of your son, who are under the protection of your son, as well as the daughters of your daughter under the protection of your daughter's husband and his family.
Leviticus 18:17 in particular covers any and all sexual relationships a man may have with a woman (who is not necessarily his wife), and seeks to protect her daughter and granddaughters from harm. While it does imply his own daughter as well, only those women who are under someone else's protection (ie. someone else's property) are genuinely protected by this law.
Later, Leviticus speaks out against father-daughter incest more specifically:
Do not profane your daughter by making her a harlot, lest the land fall into harlotry and the land become full of wickedness. (Leviticus 19:29)
The translation makes it difficult to decipher as incest, but it remains an express warning against sexual behaviour between father and daughter that the written law is unable to prevent or punish. The way this is worded (and the fact that it isn't assigned a punishment other than threatening corruption of the land) points to the main problem with the law in protecting young women and girls from their father.
A daughter is the property of her father until she marries. She lives under his protection, and her virginity is protected and preserved as a valuable commodity for her future husband. The law appears to protect a young woman during this transition from father to husband, should her virginity (and thus value) be questioned during the process:
If any man takes a wife, and goes in to her, and then spurns her, and charges her with shameful conduct, and brings an evil name upon her, saying, ‘I took this woman, and when I came near her, I did not find in her the tokens of virginity,’ then the father of the young woman and her mother shall take and bring out the tokens of her virginity to the elders of the city in the gate; and the father of the young woman shall say to the elders, ‘I gave my daughter to this man to wife, and he spurns her; and lo, he has made shameful charges against her, saying, “I did not find in your daughter the tokens of virginity.” And yet these are the tokens of my daughter’s virginity.’ And they shall spread the garment before the elders of the city. Then the elders of that city shall take the man and whip him; and they shall fine him a hundred shekels of silver, and give them to the father of the young woman, because he has brought an evil name upon a virgin of Israel; and she shall be his wife; he may not put her away all his days. But if the thing is true, that the tokens of virginity were not found in the young woman, then they shall bring out the young woman to the door of her father’s house, and the men of her city shall stone her to death with stones, because she has wrought folly in Israel by playing the harlot in her father’s house; so you shall purge the evil from the midst of you. (Deuteronomy 22: 13-18)
If this condemnation has been caused by her father, then her blood is spilt on his doorstep. But because he is the one who must produce these tokens of virginity, the incestuous father is in a position to protect both himself and his transaction.
It should be mentioned, too, that an unmarried woman is unable to accuse her father of incest, because any vow she takes can be annulled by him:
when a woman vows a vow to the Lord, and binds herself by a pledge, while within her father’s house, in her youth, and her father hears of her vow and of her pledge by which she has bound herself, and says nothing to her; then all her vows shall stand, and every pledge by which she has bound herself shall stand. But if her father expresses disapproval to her on the day that he hears of it, no vow of hers, no pledge by which she has bound herself, shall stand; and the Lord will forgive her, because her father opposed her. (Numbers 30: 3-5)
Likewise, a woman has no recourse to speak up against her husband to protect her daughter.
While the law does in fact speak against father-daughter incest, it nevertheless provides no genuine protection against it, nor punishment for anyone who commits it, because it can neither be tried nor enforced.