Rashi says that the reason he ran towards her was ‘‘because he saw the water rising towards her.’’
The Rebbe of Kuzhmir zy’a (Sefer Maamar Yechezkel) asks why he waited for the other signs. Wasn’t seeing the water rising towards her enough to know that she possessed yiras Shomayim and was worthy of marrying Avrohom’s son?
He answers that he still needed to ascertain that she was a baalas chesed. Even though he knew that she possessed yiras Shomayim, he had to know that she did chesed before he could be certain that she was worthy of joining Avrohom’s household.