Coastal Protection Models: Past, Present and Future Joe Faries

We can demonstrate and quantify the potential hazards. Hey! Those mangroves are important habitats for the ecosystem (blah blah blah) and they protect against erosion…. Coastal Vulnerability Coastal Protection Here we have a guy clearing out mangroves, THEN some ecologists step in and say you know those are a vital habitat to the marine ecosystem and they are able to explain all about that . . . Not to mention, these habitats protect against erosion. THEN coastal engineers (professional beach bums) come along and say you’re. We can demonstrate using the coastal vulnerability tool and quantify using the coastal protection tool.

Example from Belize This example highlights the abilities our tools to produce useful quantitative results in a data poor region and with diverse natural habitats which are threatened under development scenarios.

HABITATS Current Locations Specifically we will be looking at the Ambergris planning region. Ambergris Caye is a caye off the coast of northern mainland Belize. The different colors correspond to different habitats . . . I will try my best with the colors . . . . . Current Locations HABITATS Mangrove Seagrass Corals

Three development scenarios were formulated Three development scenarios were formulated. Conservation heavy essentially maintains the current state. The middle of the road is shown in the center. And the development heavy in which almost all of the caye is developed is on the RIGHT. 8.796 8.796 8.796 0.00 20.191 73.668 COASTAL DEVELOPMENT Existing Future

PROTECTION FROM STORMS Coastal Vulnerability Index Using the CV tool which was/is used in the NCA. We can quickly qualitatively assess the change in vulnerability due the habitat removal associated with development. The movement to warmer colors indicate an increase in vulnerability under different scenarios. These locations have been circled. PROTECTION FROM STORMS Coastal Vulnerability Index Low Medium High

So I am increasing the vulnerability of the coastline So I am increasing the vulnerability of the coastline . . . but what does that mean So now we got the developer thinking. . . . . That’s great but what does the increase in vulnerability really mean?

COASTAL Protection (TIER 1) That’s where the coastal protection tool comes in . . .

Surge MSL Mangrove Seagrass Coral Reef Mud or Sand So here is a diagram showing the model inputs. Our profile generator tool has the ability to extract topo bathy along a transect and place different habitats along that profile. The wave and erosion model asks for this profile and the forcing (surge and wave). The tool has the ability to investigate what happens (wave dissipation and erosion) when . . . . Habitat is removed. This is basically a sketch of most of the scenarios we were investigating in Ambergris. Coral Reef

Wave Dissipation This is an actual output from Ambergris. This represents one of the circled areas on the Northeast coast. The wave height at the shoreline (MSL) is less than half of the wave height in the case of no habitat (Role of Seagrass). The wave propagates almost twice as far inland after habitat removal (highlight Role of Mangrove). MG SG

Mud Mobilization (Erosion) With Habitat: Volumetric Loss: 0.02 m3 Erosion Distance: 03 m Without Habitat: Volumetric Loss: 1.00 m3 Erosion Distance: 79 m The importance of wave dissipation is it means lower shear stresses acting on the sediment bed. Clays and Silts mobilize when these stresses are in excess of the threshold value. The top plot shows the shear stresses with and without habitat relative to the threshold value. Using the shear stress, we plot the bed erosion rate with and without habitat (shown on the bottom). Finally, from the Bed Erosion rate and storm duration, we display volumetric loss of sediment and the distance inland of the shoreline where the sediment is mobilized.

Sand Beach Retreat Retreat With Habitat: Shoreline Retreat: 20 m Without Habitat: Shoreline Retreat: 43 m Retreat For a sandy beach, we can show the distance the shoreline retreats with and without habitat. This is an actual output further south along the East coast of Ambergris Caye.

Fetch Reefs Wave Gen Vegetation Not only are our models useful in yielding quantitative assessments of increased erosion vulnerability with development in an area that is data poor and has diverse habitats which were well received by the people we were working with in Belize, they are packed with useful tools for a sorts of more specific coastal analyses. I will show a couple examples of how we plan to break some of these tools had some minor components or modifications to yield other useful analytical models.

Marsh: Wave Erosion Stat Related to Stormy Conditions H20 < H20,crit H20 > H20,crit Salt marshes exist in sheltered basins where wind generated waves are important (Directional winds blow along fetch length). Wave heights increase with wind speed and fetch. The literature from site studies in the Gulf say that ‘H20’ is an important , specifically if H20 is > than H20,crit wave induced erosion. If it is less, non wave induced erosion.

H20 Buoy Name Year Range NOAA Buoy Wind Download Tool Estuarine Shoreline NOAA Buoy Wind Download Tool Fetch Calculator Tool Directional Fetch Distances along the Shoreline Download and Concatenate Wind Record Wind Wave Calculator Tool Depth PsuedoCode for Marsh Vulnerability Tool. Just Talk thru this If Location Adjacent to Marsh, Determine if H20 is > or < H20, Critical at that cell H20

Oyster Reef Tool Oyster Reefs are another habitat we have incorporated into the W and E model. We have extracted it and are developing it as a stand alone tool. Here you see an oyster reef blocking wave energy.

Marsh Vulnerability and Oyster Reef in Tandem 1. Identify marshes where protection is most needed. 2. Demonstrate that oyster reefs can provide the needed wave protection. Using the marsh vulnerability tool, we can identify marsh coasts that are prone to wave erosion. The oyster reef tool demonstrates that oyster reefs can protect against wave attack. We are incorporating more complete physics into the oyster reef tool such that it can advise proper design to yield desired protection. 3. Ensure that reefs are properly design to yield the desired protection.

Questions??