In an attempt to restore and preserve the natural system surrounded by the dykes and storm-surge barrier, the concept 'building with nature' was introduced in revised Delta Program updates after 2008. The new integrated water management plan not only takes into account protection against flooding, but also covers water quality, leisure industry, economic activities, shipping, environment and nature. Whenever possible, existing engineering constructions would be replaced by more 'nature friendly' options in an attempt to restore natural estuary and tides, while still protecting against flooding. In addition, building components of the reinforcements are designed in a way that they support formation of entire ecosystems. As part of the revision, the Room for the River projects, enabled nature to occupy space by lowering or widening the river bed. In order to establish this, agricultural flood plains are turned into natural parks, excavated farmland is used for wild vegetation and newly excavated lakes and bypasses create habitats for fish and birds. Along the coast, natural sand is added each year to allow sand to blow freely through the dunes instead of having the dunes held in place by planted vegetation or revetments. Although the new plan brought along additional cost, it was received favourably. The re-considerations of the Delta Project indicated the growing importance of integrate environmental impact assessments in policy-making.