FLOOD FORECASTING IN RAPID RESPONSE THE BASINS – A CASE STUDY OF THE YACUPUGRO MICRO-BASIN OF THE SLOPES OF PICHINCHA VOLCANO IN QUITO, ECUADOR

The current study presents a flood analysis methodology applicable to urban basins with concentration times less than 20 minutes, being the case of the Yacupugro micro-basin in Ecuador, which has a concentration time of 15.22 minutes, a slope of 31%, causing violent floods. The rainiest month is December, followed by February, March, November, April and January in order according to the number of frequency and probability of occurrence of floods. Since there was a lack of data on flows measured in the micro-basin, indirect hydrometeorological methods based on maximum rainfall in 24 hours and intensity, duration and frequency curves - IDF were used, allowing to compare results. Hereby, the methodology used included the analysis of hyetographs using the alternating block method, of the maximum flood flows with the rain-runoff model, besides the application of a rapid response micro-basin flood forecasting system. The Metropolitan Public Company of Potable Water and Sanitation of Quito (EPMAPS) has built a trapezoidal canal (h = 1.70 m, b = 3.80 m and m = 1.5) that collects water from the Yacupugro and Unnamed river (S/N) micro-basins, leads to a reservoir located in the San Isidro micro-basin located to its southwest of, and then deposits it in the EPMAPS sewer system. It was modeled with a total flow of 7.60 m3 / s, corresponding to a rainfall of 85.3 mm and a return period of 100 years. Thus, it was observed that the canal operates at its maximum capacity and the reservoir with its structures plates this type of floods without overflowing, fulfilling its function, if these structures are clean. The alert was based on the threshold of previous precipitation (water accumulated in the soil during the last 10, 7, 5 and 3 days), considering the type of soil to reach the field capacity reaching a depth of one meter, needing to absorb at least 129 mm of water. With this it was possible to conclude that the forecast system can start with an advance warning if the antecedent rainfall in 3 to 7 days once it exceeds 129 mm. Thus, it can be forecast well in advance of the time of concentration.