Hydrographic surveying services

Tender description

This tender is for the collection of wave characterisation data at Pevensey Bay, Sussex. The mixed, shingle barrier beach at Pevensey Bay, Sussex, represents a crucial asset in flood defence and coastal risk management along the East Sussex coastline. The 9 km frontage is highly dynamic, and suffers a net loss of sediment due to littoral drift, partly blocked by the Sovereign Harbour breakwaters. The spatial and temporal variations in beach volume, erosion and rollback remain poorly understood, and interventions to redistribute beach material are continuous. A better understanding of the dynamics of this barrier beach is needed to inform future management. The aim of the project is to measure shoreface processes, with an emphasis on wave propagation/transformation and sediment transport across the very shallow nearshore (out to approximately 5 m CD water depth). The procurement process is being conducted as an open procedure, consisting of a one stage tender process. The University proposes to enter into a contract for 18 months which includes the potential for a 6-month extension period. The data gathering will take 12 months and we may allow additional time to cover implementation or exit management issues, or delays to data gathering. The estimated value of Lot 1 is 40 000 GBP (excluding VAT). The mixed, shingle barrier beach at Pevensey Bay, Sussex, represents a crucial asset in flood defence and coastal risk management along the East Sussex coastline. The 9 km frontage is highly dynamic, and suffers a net loss of sediment due to littoral drift, partly blocked by the Sovereign Harbour breakwaters. The spatial and temporal variations in beach volume, erosion and rollback remain poorly understood, and interventions to redistribute beach material are continuous. A better understanding of the dynamics of this barrier beach is needed to inform future management. The aim of the project is to measure shoreface processes, with an emphasis on wave propagation/transformation and sediment transport across the very shallow nearshore (out to approximately 5 m CD water depth). Lot 1: Provision of Radar Services (or approved equivalent) for wave characterisation data for Pevensey Bay. Installation, maintenance and operation of a synoptic radar system or equivalent at the PCDL office, capable of delivering wave field data (including wave heights, periods, direction, and spectral properties) and surface current data for a duration of 12 months at a recording frequency of 15 minutes. The system must store and provide access to raw data such that further data service products may be derived if needed in the future. The system must be able to provide data to a distance of at least 2 km and preferably 4-6 km from the shoreline. The directional wave/current data must be gridded to a spatial resolution no more than 60 m Cartesian grid. This tender is for the collection of wave characterisation data at Pevensey Bay, Sussex. The procurement process is being conducted as an open procedure, consisting of a 1 stage tender process. The University proposes to enter into a contract for 18 months which includes the potential for a 6-month extension period. The estimated value of the contract is 140 000 GBP (excluding VAT). The mixed, shingle barrier beach at Pevensey Bay, East Sussex, represents a crucial asset in flood defence and coastal risk management along the East Sussex coastline. The spatial and temporal variations in beach volume, erosion and rollback remain poorly understood, and interventions to redistribute beach material are continuous. A better understanding of the dynamics of this barrier beach is needed to inform future management. The aim of the project is to measure shoreface processes, with an emphasis on wave propagation/transformation and sediment transport across the very shallow nearshore (out to approximately 5 m CD water depth). Lot 2: data on wave progression across Pevensey beach with vertical velocity and suspended sediment profiles. Installation, maintenance and operation of 2 cross-shore transects, 1,8 km long and 200 m apart, to be set up across the sandy foreshore in shallow waters with a tidal range of 6,1 m. Each transect will comprise an instrumented array to define a “sediment flux curtain”. Each array should comprise up to 5 stations to be deployed concurrently for a minimum of 1 year. These will allow the measurement of wave progression across the beach and vertical velocity and suspended sediment profiles (including a near bed point). These are detailed as follows: — the seaward-most station should be an acoustic wave and current profiling system (600 kHz or higher) capable of measuring directional (spectral) wave data (including raw surface wave elevation), and vertical (3D) velocity and co-located acoustic backscatter and for a minimum of 10 points in the vertical (or a minimum bin size of 25 cm). A near bed measurement of velocity and backscatter (acoustic/optical) is also required (no higher than 0,5 m above sea bed). Directional wave data will include, as a minimum, wave height (significant (Hs) and maximum (Hmax)); wave period (significant (Tz) and peak (Tp)), wave direction (mean and spreading), directional energy spectrum, and water level (absolute water depth and relative to chart datum). The measurement of currents (3D component, speed and direction) and acoustic backscatter must be at the same number of intervals as the waves. The data must be recorded at a sufficient frequency to allow spectral/directional data at a frequency no less than every 30 minutes, — at the other locations, each station must provide vertical (3D) velocity (as outline above) and acoustic backscatter for a minimum of 10 bins in the vertical (or a minimum bin size of 25 cm) and a near bed measurement of velocity and acoustic/optical backscatter/turbidity recorded at the same number of intervals as the waves measurements (seaward-most station). The sensors shall be placed as close to the seabed as is operationally practical, with near bed measurements expected to be no higher than 0,5 m off the seabed. All stations to be time synchronised so they measure equivalent parameters simultaneously, and be time stamped. Processed data to be delivered in ascii format. Time series shall be continuous (or in burst mode) and monotonic and on the same time base for all variables. Missing data should be uniformly flagged. The data must be retrieved and supplied to the project lead every 3 months, with compensation for any downtime. Loss of data, for any reason, shall not exceed 5 days in any month and cumulatively shall be no more than 45 days in a year.