Falling Damage

hey guys. i have a health bar script and i want it to lower the health when my character lands from a high place. here's the script:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerHealth : MonoBehaviour {
     public int maxHealth = 100;
     public int curHealth = 100;
     
     public float healthBarLength;
 
     // Use this for initialization
     void Start () {
         healthBarLength = Screen.width / 2;
     }
     
     // Update is called once per frame
     void Update () {
         AddjustCurrentHealth(0);
     }
     
     void OnGUI() {
         GUI.Box(new Rect(10 ,10, healthBarLength, 20), curHealth + "/" + maxHealth);
     }
     
     public void AddjustCurrentHealth(int adj) {
         curHealth += adj;
         
         if(curHealth < 0)
             curHealth = 0;
         
         if(curHealth > maxHealth)
             curHealth = maxHealth;
         
         if(maxHealth < 1)
             maxHealth = 1;
         
         healthBarLength = (Screen.width / 2) * (curHealth / (float)maxHealth);
     }
 }

do u think some c# code would do the trick? thanks