Flood Finder Chad 2017

Transcription

1 Flood Finder Chad 217 Bulletin N October 217 Flood Finder alert system is operational using observed water level data. Based on hydrological forecast, flood alerts are issued at N DJamena, Bongor, Lai, Moundou and Sarh stations one week before. Flood Alerts during 18 to 24 October is No Warning At N Djamena, Bongor,Lai, Moundou and Sarh This bulletin provides static maps showing the variation of accumulated rainfall and anomaly during the period 11 to 17 October and forecast rainfall and anomaly during 18 to 24 October in Chari and Logone river basin. It contains also detailed information on the observed and forecasted water discharge levels for the locations of N Djamena, Bongor, Lai, Moundou and Sahr. Alert Level: Severe Flood Warning: Expect serious flood and imminent danger to life and property. Flood Warning: Expect flooding that will cause disruption. Flood Watch: Possibility of some flooding. No Warning: No flood warning is in force.

2 Accumulated Rainfall Analysis (11 to 17 October, 217) The maps below shows 1) the spatial distribution of the accumulated rainfall between 11 to 17 October over the Chari/Logone Basin, and 2) the spatial distribution of rainfall anomalies during the same period. The anomaly is shown in millimeters per day (mm/d). A value of 1 mm/d would indicate that the average daily rainfall in a given week has exceeded normal rainfall by 1mm. Predominantly, rainfall between 2 to mm has occurred in the South of Chad basin, along with few places received to 1 mm especially upstream of Sarh and Moundou gauging stations, which is an anomaly upto 1 mm/day. Rainfall of 1 to 2 mm was also received upstream of Sarh which is an anomaly of 1 to 2 mm/day. Overall rainfall occurred during this week was much less than the previous week and was less than the forecast rainfall during the previous week. 2

3 Forecast Rainfall Analysis (18 to 24 October, 217) The maps below shows 1) the spatial distribution of the forecast rainfall between 18 to 24 October, 217 over the Chari/Logone Basin, and 2) the spatial distribution of forecast rainfall anomalies during the same period. The anomaly is shown in millimeters per day (mm/d). A value of 1 mm/d would indicate that the average daily rainfall in a given week has exceeded normal rainfall by 1 mm. During the next 7 days, about 2 to 1 mm rainfall is expected in the South of the basin, almost near the basin boundary, which is an anomaly of upto 1 mm/day. Remaining areas in South of the basin are expected not to receive any rainfall, which is below normal rainfall. Overall the rainfall forecasted during the next 7 days, is much less than what is received during previous week. 3

4 Flood Alert on Logone Bongor: No Warning Based on observed water levels and trends provided by the Flood Finder model, the forecast flow rate of the Logone is expected to decrease gradually until 24 October in Bongor. The Logone's water level should reach 34 cm, 6 cm below the warning level of 4 cm. During the next 7 days, the Flood alert for Bongor is No Warning of Forecast Estimated Average past 7 days Flood Alert Forecast Average for next 7 Days Discharge Trend 18/1/ No Warning 966 Overall decrease in flow by 24 % 4 Observed Bongor station in 212 and 217, Estimated and Forecast (217) Logone River Sep 6 Oct 29 Sep 22 Sep 1 Sep 8 Sep 13 Oct 3 Nov 27 Oct 2 Oct Observed (1 Sep 17 Oct,217) Estimated (13 Sep 17 Oct, 217) Forecast (18 24 Oct, 217) Nov 17 Nov 24 Nov Return Period 2. Year Return Period Year Alert_Level_Discharge 4

5 Flood Alert on Logone Lai: No Warning Based on observed water levels and trends provided by the Flood Finder model, the forecast flow rate of the Logone is expected to decrease gradually until 24 October in Laï. The Logone's water level should reach 3 cm, 144 cm below the warning level of 494 cm. During the next 7 days, the Flood alert for Lai is No Warning. of Forecast Estimated Average past 7 days Flood Alert Forecast Average for next 7 Days Discharge Trend 18/1/ No Warning 767 Overall decrease in flow by 21 % Observed Lai station in 212 and 217, Estimated and Forecast (217) Logone River Jul 7 Aug 14 Aug 21 Aug 28 Aug 4 Sep 11 Sep 18 Sep 2 Sep 2 Oct 9 Oct 16 Oct 23 Oct 3 Oct 6 Nov 13 Nov 2 Nov 27 Nov Observed (1 Sep 9 Oct,217) Estimated (13 Sep 17 Oct, 217) Forecast (18 24 Oct, 217) 212 Return Period 2. Year Return Period Year Alert_Level_Discharge

6 Flood Alert on Chari Sarh: No Warning On the basis of observed water levels at Sarh, the flow rate in Chari river is expected to decrease gradually. The Chari's water level should reach 68 cm during next 7 days. During the next 7 days, the Flood alert for Sahr is No Warning, based on the observed water levels. 12 Observed Sarh station in 212 and 217 Chari River Nov 17 Nov 1 Nov 3 Nov 27 Oct 2 Oct 13 Oct 6 Oct 29 Sep 22 Sep 1 Sep 8 Sep 1 Sep Observed (1 Sep 17 Oct,217) 212 Return Period 2. Year Return Period Year 6

7 Flood Alert on Chari N Djamena: No Warning Based on observed water levels and trends provided by the Flood Finder model, the forecast flow rate of the Chari should continue to increase gradually next week to move closer to the alert level. However observed water level on 17 October, 217 was 647 cm, about 13 cm less than the warning level of 7 cm. During the next 7 days, the Flood alert for N Djamena is No Warning. of Forecast Estimated Average past 7 days Flood Alert Forecast Average for next 7 Days Discharge Trend 18/1/ No Warning 3436 Overall increase in flow by 8 % Observed N'Djamena station in 212 and 217 Chari River Nov 17 Nov 1 Nov 3 Nov 27 Oct 2 Oct 13 Oct 6 Oct 29 Sep 22 Sep 1 Sep 8 Sep 1 Sep Observed (1 Sep 17 Oct,217) Estimated (4 17 Oct, 217) Forecast (18 24 Oct, 217) 212 Return Period 2. Year Return Period Year Return Period 1 Year Alert_Level_Discharge 7

8 Flood Alert on Logone Moundou: No Warning On the basis of observed water levels and trends provided by the Flood Finder model, the forecast flow rate of the Logone is expected to decrease gradually until 24 October in Moundou. The Logone's water level should reach 28 cm. During the next 7 days, the Flood alert for Moundou is No Warning. of Forecast Estimated Average past 7 days Flood Alert Forecast Average for next 7 Days Discharge Trend 18/1/ No Warning 46 Overall decrease in flow by 14 % Observed Moundou station in 212 and 217, Estimated and Forecast (217) Logone River Jul 7 Aug 14 Aug 21 Aug 28 Aug 4 Sep 11 Sep 18 Sep 2 Sep 2 Oct 9 Oct 16 Oct 23 Oct 3 Oct 6 Nov 13 Nov 2 Nov 27 Nov Observed (1 Sep 17 Oct,217) Estimated (13 Sep 17 Oct, 217) Forecast (18 24 Oct, 217) 212 Return Period 2. Year Return Period Year 8

9 Data sources: - Accumulated rainfall is from Global Satellite Mapping of Precipitation (GSMAP) of JAXA/EORC, Japan. More details are available at - Accumulated rainfall anomaly is calculated using the normal rainfall data of climate change knowledge portal of World Bank. More details are available at Code=TCD - Forecast Rainfall is from Global Forecasting System of NOAA, USA. More details are available at - Forecast Rainfall Anomaly is calculated using the normal rainfall data of climate change knowledge portal of World Bank. More details are available at Code=TCD Disclaimer: This is a preliminary analysis based on forecasting models and satellite based observations and has not yet been validated in the field. It is important to note that there are limitations in these data sources, and flood warnings included in this report should be treated with caution. The depiction and use of boundaries, geographic names and related data shown here are not warranted to be errorfree nor do they imply official endorsement or acceptance by the United Nations. Please send ground feedback to UNITAR UNOSAT. This flood bulletin has been produced by UNITAR-UNOSAT with the collaboration of: Ministère de l Eau et de l Assainissement du Tchad (Field data) CIMA Research Foundation (Hydrological forecast) UNICEF with funding from: European Civil Protection and Humanitarian Aid Operations (ECHO) UNITAR / UNOSAT Contact: unosat@unitar.org Ph : (UNOSAT Operations), 24/7 hotline: