Overview

This tool has been built to provide initial, remote sensing based estimates of coastal hydrology for mangrove restoration. It assesses sites for their inundation frequency on a 10 metre resolution, checks for tidal connectivity, checks for the local correlation with tidal models, checks the local tidal regime, and estimates (as a very high level approximation) which sites could be suitable habitat for mangroves.

Coastal environments are very dynamic and are generally always in some state of change, for this reason, the historical presence of mangroves is not always sufficient evidence that a site's current conditions are suitable for mangrove establishment. This can be due to natural shifting coastlines changing local topology and therby inundation patterns, human induced changes such as channels, levees, aquaculture ponds or upstream changes in river flow, and many other factors. As a first step for any restoration intervention, the current site condition and dynamics need to be well understood, and this remote sensing based hydrology assessment supports site investigations.

This tool is intended for initial, high level checks of site suitability for restoration, highlighting potential hydrological concerns. The estimates are based on satellite data, and can only augment local site data, not replace it. Always refer to local data sources and community knowledge before committing to any restoration actions such as mangrove planting or hydrological restoration.

Note that this analysis only works for open, exposed areas. Areas with existing vegetation and canopy will not be accurately mapped (and will interfere with values on the edges of open areas). The remote sensing hydrological estimates under the canopy are possible to some extent, however require local site data for callibration and verification.

For a starting point for best practices for mangrove restoration, refer to the best practice guidelines for mangrove restoration from the Mangrove Action Project.

For more information on detailed site feasibility assessment, implementing field data for science backed site suitability assessment, contact Inverto Earth.

Input

As input, you need to provide a region of interest and the analysis date ranges. The region of interest should be larger than a single specific project polygon, to capture larger tidal connectivity signals.

Input polygon requirements: - Area between 10ha and 15000ha - Single polygon - Close to the coast - Coverage of deep water, intertidal and land areas (to ensure most robust results)

For the analysis date range, this is the dates for which the analysis is performed. To robustly estimate inundation and minimise seasonal effects, at least 1 year range is recommended. A longer date range (over multiple years) can give more reliable estimates, particularly in cloudy areas, however longer date ranges also require longer processing and average out the most recent state of the coastline (recent erosion or storm damage would be less visible). Coastal environments are very dynamic and are often changing, so shorter date ranges can be better at capturing the coastline state at a specific point in time, but likely will have more noise or transient effects. The ideal choice of date range depends on the goals of the analysis, but the default of 2 years is a reasonable starting point.

It is also important that the input polygon covers enough of the intertidal area, as this is used to estimate the tidal connectivity. The image below shows an example of input which will not generate accurate tidal connectivity results, as it does not overlap any open intertidal area and only covers a small, single project boundary polygon.

The image below shows a better example, it captures both terrestrial and deep water and ensures a robust estimation of tidal connectivity within the results.

Generated output

The tool may take an hour or more to run the analysis, as it requires processing hundreds of images per site. On completion, the tool delivers the following: - A set of map layers, viewable on the results page and downloadable as GeoTIFFs - A PDF report with methodology notes and summary statistics - An email notification when the analysis finishes

The map layers are described on their own pages in this guide:

Page	Description
Inundation Percentage & Margin of Error	How often each part of the site is inundated, and the statistical confidence in that estimate
Tidal Connectivity	An index to identify where the local inundation aligns with the rest of the region, highlighting regions with tidal connectivity
Tidal Correlation	This measures how strongly the tide model correlates with the measured inundation, assesses how reliable the tidal model performs in the region
Mangrove Viability Index	A combined suitability score for mangrove restoration as high level estimate
Erosion/sedimentation indication	Indicates signs of erosion or sedimentation based on last 3 years of data
Tidal Cycle	Shows range of modelled tidal regime

Analysis steps

1. Submit — draw a boundary on the map, or upload a shapefile (.zip containing .shp/.shx/.dbf/.prj), pick a date range, and enter your email.
2. Validation conditions — based on the size of the polygon and a very rough coastline shape, this rejects polygons too large, small or too far from the coast.
3. Analysis — Satellite scenes are searched for the AOI and date range, filtered for cloud cover, and processed into the layers listed above.
4. Results — you're emailed a link to the results page once processing finishes, showing the map layers with a legend, and links to download the PDF report and all outputs as TIF files.

Hydrology and mangroves

Site hydrology is the single most critical factor for mangrove restoration success. Mangroves require an intertidal water flow, with regular inundation, that is not too dry or too wet (leading to drowning). The precise hydrological conditions for local mangrove species can vary (some species grow better lower in the tidal tables, some higher, some can handle higher salinity), so local knowledge is critical. With fine scale assessments of local natural mangrove habitats and analysis of their tidal regimes, these decisions can be made with more confidence. For tips and assistance in planning local data collection for verifying local hydrology, mapping local species habitat preferences and more, please contact Inverto Earth.