Since we know that triangles \( \triangle ABC \) and \( \triangle BAD \) are congruent, it follows that corresponding sides are equal.
Given:
- \( AC = 8 \) m
- \( AB = 17 \) m
From the congruency of the triangles, we can deduce that:
- \( AB \) corresponds to \( AD \)
Thus, we have: \[ AD = AB = 17 \text{ m} \]
Therefore, the length of \( AD \) is \( \boxed{17} \) m.