USGS Proposal: Predicting the Resilience of the Chandeleur Island Chain as a Function of Restoration Options

Task 1: Shoreline and topographic change

1. A detailed shoreline history and storm history of the Chandeleur Islands from the late 1800’s to 2006, including detailed surveys pre- and post-Katrina, will be compared for magnitude of island change and storm history. Much of the required aerial data is in house; processing and labor required for analysis is requested.
   
   
2. We will use existing LIDAR data over the Chandeleur Islands to determine how the surface area and elevations of the island have changed with time. Specifically, we will use the four LIDAR surveys conducted over the 13 months following Katrina’s landfall to assess the degree to which the islands are recovering or continuing to degrade. Initial analyses suggest that in the months immediately following Katrina, the islands continued to erode with as much as 100 m of shoreline retreat. These LIDAR flights will enable us to calculate beach profile shape, calculate changes in beach cross section, and estimate fill volume. Estimates of total volume of sand remaining in the system, including the sub-aqueous portion, are needed to assess maintenance and re-nourishment requirements of projects and future system nourishment needs. We will combine current LIDAR data with existing historical data based on non-LIDAR methodologies and create as full a view as possible of how the island area has changed over the past 100 or more years, and during previous hurricanes such as Camille. Funding will be sought within USGS for additional LIDAR surveys deemed necessary.
   
   
3. The combined LIDAR and profile survey data will be used to develop high-resolution digital terrain models of the barrier islands to aid project design and assessment of constructed projects. The models will be especially useful to
   
   
   1. quantify topographic and bathymetric changes along entire barrier island chains and within potential restoration project areas;
   2. manage sediment on an island scale rather than only a project scale;
   3. establish vertically-derived shoreline positions; and
   4. identify seasonal and storm-induced changes to beach and island cross sections, such as dune breaches and other areas vulnerable to overwash.
      

Specific variables that will be generated from the digital terrain models are:

1. barrier island length;
2. barrier island width;
3. barrier island height;
4. barrier island volume; and
5. area of subtidal, intertidal, and supratidal habitats.