sluice dokkumer nieuwe zijlen, friesland, holland

architectural architecture bridge building canal civil connect connecting construction control controlling dokkumer dokkumerdiep door doors drainage dutch engineer engineering europe european floodgate friesland frisian grootdiep holland infrastructure landmark lauwersmeer level lock mirror mirroring natural nature netherlands new nieuwe outdoor outdoors outside protect protecting railing rising river safe safety separate separating sluice sluices surface technique technology tidal tide water waterlevel watermanagement waterwork waterworks weir wet zijlen