3D grids of Hastings Beach

Continuous data is collected every summer and is used to create a 3D plan of the beach surface; a Digital Ground Model (DGM).  This DGM is then used to compared year to year data by overlaying the two data sets and creating a difference model.

To establish a ‘long-term’ review of trends in erosion and accretion along the Hastings frontage in terms of beach material volume changes, the most recently available complete DGM from 2010 has been compared to the earliest available baseline data (summer 2003) to create a difference model showing overall material gains and losses.

By overlaying and subtracting the 2003 DGM from the 2010 DGM, comparative volumetric analysis can be undertaken to determine change over the given period. Through the use of three-dimensional ground models and ortho-rectified aerial photography, it is possible to create a visual interpretation of the volumetric change that has occurred during each analysis period. This is shown in Figure 1, which indicate areas of net erosion or accretion (N.B. a 0.25m difference in elevation is considered as “no change”) and the location of any extraction/deposition sites.

Sections of beach highlighted in red represent erosion that has occurred between 2003 and 2010, and the areas highlighted blue indicate accretion. Whilst it shows an overall change in beach volume within each discrete section, it should be recognised that the data is based on the BMP survey, which is undertaken once each year. It is therefore only a snapshot of one moment in time, and the particular dynamics of each frontage need to be taken into account. This ensures that the information shown in the difference models represents the net change rather than capturing a particular extreme variation caused by a large event.

Figure 1: An example of a Difference Model, created from 2010 and 2003 DGMs

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