Methodology — FloodKH

Flood Risk Classification Methodology

FloodKH uses a deterministic, rule-based scoring system that combines multiple data sources into a composite risk score (0-100) for each of Phnom Penh's 14 districts.

Disclaimer: FloodKH is an independent monitoring tool for informational purposes only. It is NOT an official warning system. Always follow guidance from the National Committee for Disaster Management (NCDM) and local authorities.

Alert Levels

Level	Label	Score	Description
0	NORMAL	0-20	No flood risk. Normal conditions.
1	WATCH	21-45	Elevated conditions. Heavy rain expected or soil saturating.
2	WARNING	46-80	High flood risk. Flooding likely in low-lying areas.
3	EMERGENCY	81-100	Critical flood risk. Flooding imminent or active.

Scoring Components

1. Rainfall Score (max 35 pts)

7-Day Cumulative (mm)	Points
< 30	0
30-80	5
80-150	12
150-250	20
> 250	25

72h Forecast Total (mm)	Points
< 20	0
20-50	3
50-100	6
> 100	10

Flash flood bonus: +5 pts if any hourly forecast exceeds 30 mm/h.

2. Soil Moisture Score (max 15 pts)

Soil Moisture (0-7cm)	Points
< 0.30	0
0.30-0.50	3
0.50-0.70	7
0.70-0.85	11
> 0.85	15

+3 pts if soil moisture trend is rising over past 48h.

3. River Discharge Score (max 20 pts)

Discharge Ratio (current/avg)	Points
< 1.0	0
1.0-1.3	4
1.3-1.6	9
1.6-2.0	15
> 2.0	20

+5 pts during Jun-Oct when Tonle Sap reverse flow is active.

4. Satellite Score (max 15 pts)

Flood Fraction (%)	Points
< 2%	0
2-5%	4
5-10%	8
10-20%	12
> 20%	15

Currently simulated from rainfall data. Real Sentinel-1 SAR integration planned.

5. District Vulnerability (max 15 pts)

Static score: drainage quality (0-12 pts) + flood history (0-3 pts) + low elevation bonus (+2 if <10m).

72-Hour Prediction

Future risk estimated by replacing observations with forecasts. Soil moisture extrapolated at +0.05/day (rising) or -0.03/day (falling). Confidence: High (T+24h), Medium (T+48h), Low (T+72h). Uncertainty widens 10% per step.

Data Sources

Source	Provides	Status	Frequency
Open-Meteo	Precipitation, soil moisture, forecasts	Live	6 hours
Open-Meteo Flood	River discharge (GloFAS)	Live	Daily
Sentinel-1 SAR	Water extent	Stub	~6 days
Sentinel-2	NDWI water index	Stub	~5 days
NASA GPM IMERG	Satellite rainfall	Stub	30 min

Limitations

District boundaries are approximate
Satellite sources currently simulated
Urban microflooding not captured
Predictions beyond 24h carry significant uncertainty
Not a replacement for official flood warnings