Flood warning sirens. There are loads in lincolnshire.
From the essex flood plan 2002:
Flood Warning Sirens – There are 36 Tidal Flood Warning Sirens which are positioned in the coastal areas most likely to be affected (see Annex D, Section III). The warning is given by FIVE THIRTY SECOND SOUNDINGS AT FIFTEEN SECOND INTERVALS. (Activated by ECC, see Annex F, Section III)
TIDAL FLOOD WARNINGS
SIREN LOCATIONS
TENDRING DISTRICT COUNCIL
HARWICH POLICE STATION
PARKESTON QUAY HAMILTON HOUSE
WALTON ON NAZE CAR PARK
JAYWICK SANDS MIDWAY
JAYWICK FROBISHER DRIVE
JAYWICK LION POINT
ST. OSYTH POINT CLEAR
BRIGHTLINGSEA FIRE STATION
COLCHESTER BOROUGH COUNCIL
WEST MERSEA FIRE STATION
WIVENHOE FIRE STATION
WIVENHOE PHILLIP ROAD
MALDON DISTRICT COUNCIL
HEYBRIDGE ECC H/WAYS DEPOT
MAYLANDSEA NIPSELLS CHASE
ST LAWRENCE BAY ST LAWRENCE DRIVE
BURNHAM ON CROUCH POLICE STATION
BURNHAM ON CROUCH CLOCK TOWER
SOUTHMINSTER POLICE STATION
TILLINGHAM FIRE STATION
TOLLESBURY RECREATION GRND
CHELMSFORD BOROUGH COUNCIL
S.W.F FIRE STATION
S.W.F TELEPHONE EX.
S.W.F GLADDEN FIELDS
ROCHFORD DISTRICT COUNCIL
FOULNESS ISLAND TREE FARM, COURTSEND
HULLBRIDGE RECREATION GROUND
CASTLE POINT BOROUGH COUNCIL
SOUTH BENFLEET POLICE STATION
CANVEY ISLAND CANVEY ROAD
CANVEY ISLAND NORTHWICK PARK SCHOOL
CANVEY ISLAND FIRE STATION
CANVEY ISLAND POPLAR ROAD
CANVEY ISLAND MAURICE ROAD
CANVEY ISLAND RATTWICK DRIVE
CANVEY ISLAND NEWLANDS ROAD
CANVEY ISLAND CLIMMEN ROAD
CANVEY ISLAND PLAYING FIELD
(OFF STATION PARADE)
THURROCK BOROUGH COUNCIL
TILBURY OLD FIRE STATION
GRAYS ORSETT ROAD
http://www.essexcc.gov.uk/vip8/ecc/ECCWebsite/content/binaries/documents/Floodplan_2002_final.pdf
Hope this helps
Rob...