Past Floods

On 14 December 2020, the CyFFORS flood forecasting system was activated based on the meteorological forecast that issued on the previous day (13 December 2020). Figure 1 illustrates the simulated discharge across the Rafina stream on 14 December 2020 at 06:00 UTC (08:00 local time). The highest values of discharge exceeding 10 m3/s were forecasted in the stream section that passes through the Rafina residential area, close to the stream’s outlet.

Figure 1: Streamflow forecasting map for Rafina stream basin (Attica, Greece), valid for 14 December 2020 at 06:00 UTC (08:00 local time).

According the preliminary warning thresholds, which were defined according to the hydrometeorological and socio-economic impact analysis that conducted in the framework of CyFFORS in the area [1], this exceedance corresponded to possible minimal impacts (Table 1). For this, a flood alert associated with this expected level of impact was issued, as shown in Figure 2. This warning corresponds well to the localized flooding reported in the area by the local media (https://www.irafina.gr/rafina-afti-ine-i-katastasi-stis-gefires-tis-arionos-ke-tou-varda-pou-plimmirisan-apo-tin-kakokeria-foto/).

Table 1. Socioeconomic impact intensity classification.

 

I0: Minimal

I1: Minor

I2: Significant

I3: Severe

Human life

Not expected

Risk for vulnerable groups of people and/or involved in endangered situations

Danger to life due to physical hazards associated with flooding water

Danger to life due to physical, chemical and utility hazards associated with flooding water

Damage to properties and public structures

Not expected

Light damage to individual properties

Important damage to many properties and/or public structures

Extensive damage to multiple properties and/or public structures

Transportation

Little or no disruption to river crossings and/or roads close to the river/stream

Small-scale disruption (local and short term)

Large-scale disruption (broad and long term) and/or important damage to the transport network

Extensive disruption (broad and long term) and/or extensive damage to the transport network

Utilities

Not expected

Small-scale disruption (local and short term)

Large-scale disruption (broad and long term)

Extensive disruption (broad and long term) and/or loss of utilities

Figure 2: Hydrograph forecast for the Rafina stream basin outlet (Attica, Greece), issued on 13 December 2020).

The encouraging performance of the CyFFORS flood forecasting system is also supported by the observed and modeled rainfall time series in the Rafina meteorological station. As can be seen in the Figure 3, the WRF-Hydro-simulated rainfall was close to the observed one in terms of both timing and intensity.

Figure 3: Time series of the observed and WRF-Hydro-modeled rainfall over the Rafina meteorological station from 14 December 2020, 00:00 UTC, to 15 December 2020, 00:00 UTC

[1] Giannaros, C.; Kotroni, V.; Lagouvardos, K.; Oikonomou, C.; Haralambous, H.; Papagiannaki, K. Hydrometeorological and Socio-Economic Impact Assessment of Stream Flooding in Southeast Mediterranean: The Case of Rafina Catchment (Attica, Greece). Water 2020, 12, 2426. DOI: 10.3390/w12092426