Land Area Inundated by Scenario
Population at Risk by Scenario
Top 10 Most Vulnerable Islands , Current Scenario
Flood Exposure Map
Island Vulnerability Rankings
| Rank | Island | Atoll | Area (km ) | Population | % Land | Pop. at Risk | VI Score |
|---|
Historical Sea Level + ML Projections to 2100
Model Accuracy on Held-Out Test Period
ML Model Performance , All 8 Models
F1 Score & Skill Score , Visual Comparison
Methodology & Data Sources
Phase 1: GIS Flood Inundation
Static bathtub model applied to SRTM 30m DEM data across all 181 inhabited Maldivian islands. Island elevation profiles are parameterised by mean elevation, maximum elevation, and fraction of land below 1m. Flood inundation is computed for 5 IPCC AR6 scenarios including a compound storm surge scenario.
Phase 2: Machine Learning Sea Level Prediction
Eight models trained and evaluated on 38 years of UHSLC tide gauge data (Station 108, Mal , 1988-2026). The Hybrid LSTM incorporates real NOAA monthly ONI and DMI climate indices as exogenous predictors. An 80/20 chronological train/test split was used; all models evaluated on identical held-out test set.
| Model | RMSE (cm) | R | Framework |
|---|---|---|---|
| Ensemble (LSTM+Hybrid) | 4.37 | 0.535 | Pure JS Best |
| Hybrid LSTM (MSL+ONI+DMI) | 4.38 | 0.534 | Pure JS |
| LSTM (univariate) | 4.58 | 0.490 | Pure JS |
| Random Forest | 5.61 | 0.235 | Python/sklearn |
| Gradient Boosting | 5.98 | 0.130 | Python/sklearn |
| XGBoost | 5.99 | 0.128 | Python/XGBoost |
| ARIMA(1,1,0) | 11.90 | -2.44 | Pure JS |
| Prophet (additive) | 10.18 | -1.52 | Pure JS |
Phase 3: Dashboard
Node.js/Express server with Chart.js and OneMap API frontend. All outputs pre-computed as JSON files in outputs/. Deploy with node server.js.
Data Sources
| Dataset | Source | File |
|---|---|---|
| Monthly Sea Level | UHSLC Station 108 | data/male_sealevel.csv |
| ONI Index | NOAA CPC | data/oni.csv |
| DMI Index | NOAA PSL | data/dmi.csv |
| Island registry | OneMap ArcGIS FeatureServer | data/islands.json |
| Elevation DEM | NASA SRTM | Parameterised |
Run the Analysis
npm install && pip install -r requirements.txt npm run analyse # LSTM models npm run analyse:advanced # RF + GB + XGBoost node server.js # Dashboard at http://localhost:3000
International Context
How does this study compare to similar work in other countries? Four comparison groups are presented below.
Pacific Small Island States
Storlazzi et al. (2018) modelled wave-driven flooding for Pacific atoll islands using a physics-based Boussinesq wave model. That study achieves higher physical accuracy but covers three islands. This framework covers all 181 inhabited Maldivian islands using a simpler bathtub model , a deliberate trade-off of precision for national coverage. The 38-year Male tide gauge record is also substantially longer than most Pacific records (typically 20 to 25 years), giving the ML component a meaningful training data advantage.
For Kiribati, Tuvalu and the Marshall Islands most national assessments use CMIP6 projections downscaled to individual islands rather than ML forecasting from local station records. The integrated ML-plus-GIS approach used here has not been applied at national scale to any Pacific SIDS.
Bangladesh FFWC , Closest Operational Equivalent
The Bangladesh Flood Forecasting and Warning Centre (FFWC) has deployed LSTM-based models for real-time tidal and river level forecasting (Kabir et al., 2020). Their published RMSE for tidal station predictions is 3 to 6 cm , directly comparable to the Ensemble RMSE of 4.37 cm achieved here. The key difference is that the FFWC system runs on live government servers with real sensor feeds and issues operational alerts. This dashboard uses pre-computed outputs. The implication is that the Maldives has the technical building blocks for an equivalent operational system.
Netherlands and Australia
The Netherlands uses Deltares Delft3D hydrodynamic models for coastal flood simulation, incorporating wave dynamics, storm surge and bathymetric data at fine resolution. This achieves higher physical accuracy but requires national LiDAR coverage, high-resolution bathymetric surveys and substantial computing infrastructure , none of which exist at national scale for the Maldives.
Australia's National Coastal Vulnerability Assessment (DCCEE, 2011) is the closest structural parallel: a national-scale vulnerability index producing ranked coastal segments. Australia uses a six-variable scoring system compared to the three-variable VI used here. This framework adds the ML forecasting component and the live OneMap API integration, neither of which appear in the Australian assessment.
Key Differentiator
Across all comparison groups, the unique contribution of this study is the combination of three things that have not previously been integrated: ML sea level forecasting from a long local tide gauge record, national-scale GIS vulnerability ranking for all inhabited islands, and live government data API integration via OneMap. Each component individually has precedents. Their combination in a SIDS context does not.
How This Study Compares
| Study / System | Country | Approach | Islands / Scale | ML Component |
|---|---|---|---|---|
| This study | Maldives | Bathtub GIS + LSTM Ensemble | 181 islands national | 8 models, RMSE 4.37 cm |
| Storlazzi et al. (2018) | Pacific SIDS | Boussinesq wave model | 3 islands | None |
| Kabir et al. / FFWC | Bangladesh | LSTM tidal forecasting | Operational stations | RMSE 3-6 cm |
| Deltares / Delft3D | Netherlands | Hydrodynamic model | National | None |
| DCCEE (2011) | Australia | 6-variable VI assessment | National coastline | None |
| Amores et al. (2021) | Maldives | Wave-driven inundation | Selected islands | None |
Glossary
Definitions for all technical terms used in this dashboard and the accompanying dissertation.
Model Performance Metrics
| Term | Full Name | What it means |
|---|---|---|
| RMSE | Root Mean Square Error | Average prediction error in centimetres. Lower is better. The Ensemble achieves 4.37 cm on the 85-month test set. |
| MAE | Mean Absolute Error | Average absolute error in centimetres. Less sensitive to large outliers than RMSE. |
| R^2 / NSE | R-squared / Nash-Sutcliffe Efficiency | How much of the observed variance the model explains. 1.0 = perfect, 0 = no better than predicting the mean, below 0 = worse than the mean baseline. |
| MAPE | Mean Absolute Percentage Error | Error as a percentage of the mean absolute anomaly (5.11 cm). Lower is better. |
| Skill Score | Skill Score vs persistence | Improvement over a naive forecast that simply predicts last month's observed value. Above 0 means better than persistence. The Ensemble scores 0.07 (7% better than persistence baseline). |
| F1 Score | F1 Score | Accuracy of detecting months when sea level exceeds the +8 cm anomaly threshold. Balances precision (avoiding false alarms) and recall (catching real events). 1.0 = perfect, 0 = no skill. |
| Precision | Precision | Of all the months the model flagged as dangerous, what fraction actually were. High precision = few false alarms. |
| Recall | Recall | Of all the genuinely dangerous months, what fraction the model correctly identified. High recall = few missed events. |
Machine Learning Models
| Term | Full Name | Description |
|---|---|---|
| LSTM | Long Short-Term Memory | A recurrent neural network architecture that can retain information over long time periods. Used here in univariate form with only sea level as input. |
| Hybrid LSTM | Hybrid LSTM (MSL + ONI + DMI) | LSTM model using three input features per timestep: sea level, ONI, and DMI. The climate indices provide a 3-6 month lead time signal. |
| Ensemble | Ensemble (0.6 LSTM + 0.4 Hybrid) | Weighted average of LSTM and Hybrid LSTM predictions. Best-performing model in this study (RMSE = 4.37 cm, F1 = 0.59). |
| ARIMA | AutoRegressive Integrated Moving Average | Classical statistical time series model. Used as a baseline. Poor performance here (RMSE = 11.90 cm) because it cannot capture non-linear inter-annual variability from ENSO and IOD. |
| Prophet | Prophet (additive decomposition) | Open-source forecasting model by Meta. Decomposes series into trend, seasonality, and residuals. Better than ARIMA but still limited on inter-annual signals (RMSE = 10.18 cm). |
| RF | Random Forest | Ensemble of decision trees. Implemented with 500 trees and lag features. Intermediate performance (RMSE = 5.61 cm). |
| GB | Gradient Boosting | Sequential ensemble of shallow trees. Intermediate performance (RMSE = 5.98 cm). |
| XGB | XGBoost | Optimised gradient boosting implementation. Similar to GB (RMSE = 5.99 cm). |
Climate and Oceanographic Terms
| Term | Full Name | Description |
|---|---|---|
| ONI | Oceanic Nino Index | Monthly index measuring El Nino and La Nina strength in the equatorial Pacific. Affects Indian Ocean sea levels via atmospheric teleconnections. |
| DMI | Dipole Mode Index | Monthly index measuring the Indian Ocean Dipole. A positive IOD event in 2019-2020 (DMI peak = 0.964 deg C, second strongest on record) produced the largest sea level anomalies in the 85-month test period. |
| IOD | Indian Ocean Dipole | A coupled ocean-atmosphere pattern in the Indian Ocean. Positive IOD events drive sea level rise across the central and northern Indian Ocean via coastal Kelvin wave propagation. |
| ENSO | El Nino-Southern Oscillation | The dominant Pacific climate mode. Affects Indian Ocean sea levels and is captured by the ONI index used in the Hybrid LSTM. |
| MSL | Mean Sea Level | The average level of the ocean surface, used as the baseline for sea level rise measurements. |
| SLR | Sea Level Rise | The increase in mean sea level over time due to ocean thermal expansion and ice melt. |
| SSP | Shared Socioeconomic Pathway | IPCC AR6 climate scenarios. SSP1-2.6 assumes strong emissions cuts; SSP5-8.5 assumes continued high emissions and projects up to +1.0m by 2100. |
| IPCC AR6 | Sixth Assessment Report | The authoritative international scientific assessment of climate change, published 2021 by the Intergovernmental Panel on Climate Change. |
Data and Methods
| Term | Full Name | Description |
|---|---|---|
| VI | Vulnerability Index | Composite score (0 to 1) for each island: VI = 0.5 x land flooded + 0.3 x normalised population + 0.2 x (1/island area). Higher score = more vulnerable. All sub-indicators normalised to [0,1] before weighting. |
| GIS | Geographic Information System | Tools and methods for spatial data analysis. Used here for flood inundation mapping of all 181 inhabited islands. |
| Bathtub model | Bathtub inundation model | Simple flood model that classifies all land below a sea level threshold as permanently inundated. Standard approach for national-scale screening where LiDAR data is unavailable. |
| SRTM | Shuttle Radar Topography Mission (+/-5--10m vertical accuracy) | NASA satellite elevation dataset at 30m resolution. Used to estimate island elevation in the absence of national LiDAR coverage for the Maldives. |
| OneMap | OneMap Maldives | The official national mapping platform of the Maldives government. Provides island boundary polygons, names, and atoll classification via an ArcGIS FeatureServer API. |
| UHSLC | University of Hawaii Sea Level Center | Maintains the 38-year tide gauge record at Male, Maldives (Station 108) used to train and test all ML models in this study. |
| ArcGIS | ArcGIS JavaScript API | Esri mapping platform used to display real OneMap island boundaries, flood bubble overlays, and reef/lagoon layers in the dashboard map. |