Indian River Lagoon Seagrass Mapping · | Indian River Lagoon Seagrass Mapping Seagrass, a submerged flowering plant found in shallow waters, provides food, habitat, and nursery areas

Indian River Lagoon Seagrass Mapping

Keith Patterson, PSM, SP, GISPSenior Project ManagerGeospatial and Technology ServicesDewberry [email protected]

TOPICS

2 | Indian River Lagoon Seagrass Mapping

• Importance

• Methods

• Results

• Trends

WHY MAP SEAGRASS?


Seagrass, a submerged flowering plant found in shallow waters, provides food,habitat, and nursery areas for numerous vertebrate and invertebrate species.

Seagrass communities are sensitive to changes in water quality.

The distribution and extent of seagrass is considered a barometer of the healthestuarine systems.

The Indian River Lagoon is considered as oneof the most biodiverse lagoonal ecosystemsin the Northern hemisphere and is home tomore than 3,000 species of plants andanimals.

PROJECT AREA – INDIAN RIVER LAGOON


The Indian River Lagoon is agrouping of three lagoons onthe Atlantic Coast of Floridathat include the MosquitoLagoon, Banana River, andthe Indian River.

AERIAL PHOTOGRAPHY ACQUISITION


Digital Imagery Acquisition


Aircraft: Cessna 206Sensor: Microsoft UltraCamX (or

similar camera) – very high resolution, large format digital camera

• Typical Imagery Acquisition Platform

Imagery Acquisition Flight Plan


Flight lines are planned according to the area of interest

• 12 inch Ground Sample Distance (GSD)

• 4- Band Imagery

• Stereo Collection

Optimal Imagery Requires Pre-flight Planning along with Daily Condition Monitoring


Pre-flight Scheduling• Weather, wind• Biomass (April – June)• Sun angle below 30 degrees (glare)

Pre-flight Water Condition Monitoring• Turbidity• Tidal influence• Water releases• Rain events• Wave height (glint)

Dewberry has a network of information providers to help with condition monitoring so that conditions are evaluated prior to flying.

Limited collection window each day

May/June: start of thunderstorm season

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When to Fly?

9 | Indian River Lagoon Seagrass MappingFlight Plan Sun Angles WeatherTides

Indian River North Lagoon 2011 Algae Bloom

Complicated Time-Sensitive Acquisition

Biomass

Algae Bloom


SEAGRASS

Imagery


Quality control is then performed to ensure the visibility of submerged features:

• Review flight logs (sun angles)• Compare new imagery to known

seagrass locations • Evaluate water clarity throughout

the project area• Conduct re-flights if necessary

Aerial imagery is acquired:• April - May • Every two years


GEOREFERENCING THE AERIAL PHOTOGRAPHY

Aerial Triangulation (AT)


PURPOSE: Removes distortion from the imagery and accomplishes georeferencing to the Earth

Inputs to the aerial triangulation solution:Airborne GPS/IMU data captured during flight records GPS position / pitch, roll, yaw (heading) of the aircraft

Photo-identifiable ground control points are collected via ground surveying and are used to improve the aerial triangulation result.

Sensor calibration information specific to the geometric properties of the camera is considered within the AT solution.

QUALITY CONTROLSpatial Accuracy Assessment


PURPOSE: Spatial accuracy is tested before mapping begins.

• Otherwise: False changes in seagrass extent could be mapped

• Surveyed “Check Points”

• Photo-identifiable features appearing on imagery are surveyed. The check points are then compared with the georeferenced imagery.

IMAGERY DELIVERABLES


ORTHOPHOTOGRAPHY

• Used primarily as a backdrop on laptops in the field and within ArcGIS during ancillary data comparison

STEREO IMAGERY

• Used for photo interpretation within photogrammetric workstations

FIELD WORK


Field Work


Purpose:

Imagery Signature Identification• Ties imagery signatures (colors, tones, texture) to

seagrass occurrence in the field • Performed during the imagery acquisition phase

Groundtruthing• Resolves photo interpretation questions and

facilitates quality control• Performed during photo interpretation

Thematic Accuracy Assessment• Tests classification accuracy• Performed after final mapping• Over 200 accuracy assessment points are used

Field Work


PROCESS:• Field points are mostly pre-selected while in the office

• The photo interpreters travel to and locate each pre-selected field point accurately via GPS.

• The seagrass at the field location is compared to the imagery and ongoing mapping using snorkeling and underwater video

• Seagrass classification and extent is documented while in the field using ArcMap.

• A Photointerpretation Key (i.e. mapping guide) is produced for use during photointerpretation so that seagrass is mapped consistently.

Field Equipment


Field Work


Fieldwork using watercraft, snorkeling, underwater video, GPS and GIS

INDIAN RIVER LAGOON SEAGRASS


PHOTO INTERPRETATION


Photo Interpretation - Change Analysis


Performed using stereo photogrammetric workstations

• Prior linework compared to new imagery and edited for seagrass changes

• Ancillary data is continually accessed• Field data • Bathymetry• Historical imagery• Satellite imagery

• Image histograms are adjusted for maximum visualization

• Mapped data is stored within ArcGIS

• Field visits are conducted during the photo interpretation phase to check habitat changes

Inputs to Decision Making – Is it a valid change?


SEAGRASS CHANGE IDENTIFIED

REVIEW 2013 IMAGERY

SIGNATURE

REVIEW 2013 LINEWORK

REVIEW ANCILLARY

GEOSPATIAL DATA AND FIELD DATA

REVIEW 2015 IMAGERY

SIGNATURE

SEAGRASS CHANGE DIGITIZED

CONSULT PI KEY

VISIT FIELD IF

NECESSARY


CLASSIFICATION CODES

5400 Unvegetated Bottom <10% cover

9113 Seagrass, Patchy

9116 Seagrass, Continuous ≥10% cover

Continuous seagrass polygons are further classified according to the percent cover of seagrass (i.e. density) existing within each polygon. 100%, 80%, 60%, 40%, 20%

NO SAV Not Classified (land, islands, mangroves, etc.)

Edge Confidence Classification:

HC High Confidence

MC Moderate Confidence

LC Lower Confidence

Photo Interpretation Editing Process


The 2013 seagrass map is updated (digitally edited) to reflect 2015 conditions:

• Ensures that only true seagrass changes are recorded within the data

• Ensures that un-changed seagrass beds remain un-changed in the data

• Allows for the generation of change maps using GIS

• Change statistics can be summarized for the project

Blue linework = 2011Purple linework = 2013

MOST IMPORTANT: The methods yield reliable maps and statistics that quantify the amount of seagrass change over time.

Mapped Seagrass Examples


Continuous Seagrass (9116)Patchy Seagrass (9113)Unvegetated Bottom (5400)

MONITORING TRANSECTS


FIELD TRANSECTS ARE MONITORED UNDER A DIFFERENT PROGRAM

• Visited yearly during the summer since 1994• Document the species, depth, density of

seagrass• Data from the transects can be used to

validate the mapping on a site-specific basis

TYPICAL MONITORING TRANSECT


Special Thanks To:LAUREN HALL, St. Johns River Water Management District - Environmental Scientist who diligently documents these transects each year and provides significant support to the seagrass mapping effort as well.

Unfortunately, the news is not good


CHANGE STATISTICS

TREND ANALYSIS


2015 ACREAGE = 58,792

2007 ACREAGE = 80,442

1992 ACREAGE = 65,032


CONTINUED MAPPING/MONITORING IS NEEDED


THANK YOU!

Keith Patterson, PSM, SP, GISPSenior Project ManagerGeospatial and Technology ServicesDewberry [email protected]

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Indian River Lagoon Seagrass Mapping · | Indian River Lagoon Seagrass Mapping Seagrass, a submerged flowering plant found in shallow waters, provides food, habitat, and nursery areas