Flushing Methods in Polder Drainage System to Obtain Better Environment Quality S. Imam Wahyudi, Robbe van de Lustgraaf, Loic de Moor, Rick Heikoop and Henny Pratiwi Adi MATEC Web Conf., 280 (2019) 03014 Published online: 08 May 2019 DOI: 10.1051/matecconf/201928003014