Monitoring Instruments & Techniques
LIDAR
Light Detection and Ranging (LIDAR) is a remote sensing system used to collect bathymetry data using
aircraft-mounted lasers capable of recording elevation measurements. This technology has been used by
CWMS to produce high resolution - 3x3m nearshore and 5x5m offshore-bathymetric map of Dubai's coastal
zone. Tenix LADS Corporation was commissioned in 2004 and 2007 to carry out those surveys using MK II System.
Echo Sounder
Conventional bathymetric surveys are conducted using Kongsberg EA 400 dual frequency (38 and 220 KHz)
single beam echo sounder mounted on a survey vessel integrated with Trimble DSM 132 DGPS. Navigational
line control and data logging are achieved by using an integrated navigation software package called
Trimble Hydropro. This enables recording positions, quality checks and depth in a time-tagged format.
HF Radar
HF RADAR deployed in Dubai is a network of two SeaSonde radial sites and one SeaSonde combining station
to produce surface current maps between Port Rashid and Umm Suqeim. The HF-RADAR system operates
on the mechanism of Bragg scattering of the electromagnetic radiation over a rough sea. This mechanism
is based on the property that an electromagnetic wave at a given frequency scatters on the ocean waves
of exactly half the wavelength. For the HF-Radars this means that a 7 m wave (corresponding to a 43.75
MHz transmitting frequency) is backscattered from the 3.6 m sea surface waves. The SeaSonde radars deployed
in Jumeirah and Umm Suqeim are operating at 43.75 megahertz and have a range between 15 and
20km. The surface current data are obtained at a spatial resolution of about 215m from shoreline to
offshore water depths down to 15-20m and are available every 30 minutes. The system is also capable
of measuring wave period, wave height, wave direction and wind speed every 10 minutes.
It should be noted that this unique technique will contribute significantly to the understanding of the
physical processes associated with the impact of waves and currents on the natural changes along the coastline.
Cameras
Ten high resolution cameras (UEye and Panasonic) are used to capture images (snap shot, average, variance
and video) of Dubai beaches at 30 min interval during day light time. These images are geo-rectified using
ground control points and image analysis is carried out using Matlab and GIS tools. The data products from
this analysis include periodical shorelines, pre and post storms (Shamal) shorelines, inter-tidal beach
profiles, location of rip currents, sand bars and wave run-up during storm events.
ADCP
Acoustic Doppler Current Profilers are used for monitoring currents and waves along the Dubai coastline.
Teledyne RDI's 1200 kHz and 600 kHz upright and 300 kHz Horizontal ADCPs are deployed at nearshore,
offshore and Creek mouth locations, respectively. A total of seven ADCPS (four nearshore, two offshore
one in the Dubai Creek) are operated by the CWMS. Nearshore ADCPs are deployed at approximately 6-8 m water
depth in a 500-kg concrete frame resting on the seabed. The ADCP frame is fitted with a 316 stainless steel
gimbal to compensate for a sloping seabed and maintains the ADCP transducers in a vertical upward orientation.
Offshore ADCPs are deployed at a depth of approximately 16-20 m, with the same system of concrete block and
gimbal. The term "bin size" is representative of the distance between vertical sampling areas monitored by an
ADCP, where nearshore ADCPs measure every 0.35 m and offshore ADCPs take current readings every 0.75 m. The
H-ADCP deployed at Dubai Creek mouth measures the cross sectional current flow through the Dubai Creek across
a range of approximately 70 m from the transducer head.
All ADCPs (except for the H-ADCP) record current speed and direction, peak wave period, significant wave
height, peak wave direction, water temperature and water level. The H-ADCP measures only water temperature,
current speed and current direction across the creek.
Water Level Sensors
Valeport 740 and 730WT models are used to record water level at six locations across the Dubai coast. The
Valeport 740 model (installed at Mina Seyahi, JBH, Creek Mouth and Dubai festival City) records water
level only (every 10 minutes) while the Valeport 730 WT model (installed at Jebel Ali and Mamzar) records
water level (every 15 minutes), wave period and significant wave height. The observed water levels are
converted to tidal elevation by accounting for Dubai Municipality Datum.
Water Quality Sensors
Two YSI 6600 V2-4 water quality sondes integrated with sensor probes to measure temperature, salinity,
chlorophyll, dissolved oxygen, and turbidity are deployed at Palm Deira offshore and Jumeirah Open Beach
nearshore buoys. The YSI sondes are moored to the buoys themselves, with the probes located, and
sampling at a depth of approximately 1 m.
DGPS
Differential GPS is used for topographic survey of the beaches. Trimble R7 and R8 receivers are used as
rovers and differential correction for these rovers are received from Dubai Virtual Reference Stations (DVRS)
through GPRS subscription.