Listen NCERT Audio Books - Kitabein Ab Bolengi
It is important to make small check dams across the flooded gullies because they:
(i) hold water for irrigation
(ii) hold water and prevent soil erosion
(iii) recharge groundwater
(iv) hold water permanently
Small check dams hold water and prevent soil erosion, they help in recharging groundwater. So they are build across flooded gullies.