Available online at ScienceDirect. Procedia Engineering 154 (2016 )

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1 Available online at ScienceDirect Procedia Engineering 154 (2016 ) th International Conference on Hydroinformatics, HIC 2016 Modeling of floods and flood control water reservoirs for evaluation of inundation Da Nang province of Vietnam. Le Hong Nhung a,*, 1 *, Perminov A.V a, Kozyr I.E. a a Russian state agrarian university - Moscow agricultural academy named after K.A. Timiryazev, Pryanishnikov St., 19, Moscow, , Russian. Abstract Monsoon rains cause floods in Viet Nam almost every year, particularly in the city of Da Nang, where the stormy rainfall has brought to almost 600 mm within one day then inundation was catastrophic. Therefore there is an urgent need to mitigate floods what can be achieved by using flood-control reservoirs. So, the main objective of the present work is to evaluate the possibility of mitigating inundations with help of modeling floods and their routing through the reservoir. The virtual water reservoirs are considered in various sites of the Han river. Accordingly, the necessary characteristics are determined on the basis of GIS information.in the work the following tasks were solved: modeling of storm rainfall; modeling scenarios of catastrophic floods on river basin; determination of characteristics for water reservoir; modeling of flood routing through water reservoir; modeling of inundation on Da Nang territory.the results provide a possibility to consider variants of the locations for the location of the flood-control reservoirs and corresponding variants of inundation in the city of Da Nang The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( The Authors. Published Elsevier Ltd. Peer-review under responsibility of of the the organizing committee of HIC of HIC Key words: stormy rainfall, inundation, modeling of flood, flood-control, water reservoir. * Corresponding author. address: hongnhungle94@gmail.com The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of the organizing committee of HIC 2016 doi: /j.proeng

2 1320 Le Hong Nhung et al. / Procedia Engineering 154 ( 2016 ) Introduction Monsoon rains cause floods in Viet Nam are very dangerous for the city of Da Nang, where the stormy rainfall can be almost 600 mm within one day then inundation will be catastrophic. Therefore there is an urgent need to mitigate floods what can be achieved by using flood-control reservoirs. So, the main objective of the present work is to evaluate the possibility of mitigating inundations with help of modeling floods and their routing through the reservoir. The virtual water reservoirs are considered in various sites before Da Nang. 2. Method and materials Usually inundations in the city of Da Nang are formed because of runoff floods of two small rivers (fig1). Fig. 1. The map of Da Nang Maximum water discharges and depths of floods depends on precipitation and on topographic characteristics of the river basins. The topographic characteristics were defined on the base of topographic map which is represented by SURFER (fig2).

3 Le Hong Nhung et al. / Procedia Engineering 154 ( 2016 ) Fig. 2. Rivers basins in program "Surfer" The necessary characteristics of river basin were defined with help "SURFER" and formulas. Modeling of storm rainfall was made on the base of data observation daily precipitation. Most dangerous model was chosen relative to inundation of city Da Nang by runoff. The precipitation value was taken equal to 600 mm, which is evenly distributed during the day. The flood runoff model is based on the formula of "intensity of precipitation" [1] for maximum water discharge: Q A H F, (1) max 1% 1% p H1% - maximum daily depth of precipitation of probability 1%; special coefficient of runoff; A1% - share of H 1%; coefficient, which takes into account the influence of lakes on the river basins; p coefficient which takes into account of other probability; F river basin square. The value H 1% has been defined according to data observation of Da Nang meteorological station and consequent probabilistic model. The coefficient was defined in dependence on several parameters: run-of-river characteristics, slope characteristics of catchments. The value of is determined by special applications [1.2] depending on the number of parameters, including hydro-morphological riverbed characteristics p, time of slope concentration and area of the catchment. m p hydraulic parameter of riverbed, L length of riverbed, km. I p slope of the river, o / oo m special parameter of riverbed. F river basin square. p 1000L 0.25 m 0.25 mp Ip F H1%, (2) Flood hydrographs (fig 3) were defined on the base of the observed inundation during 1999 year.

4 1322 Le Hong Nhung et al. / Procedia Engineering 154 ( 2016 ) Water discharges,cub m/sec Q1(t) q1(t) Q2(t) q2(t) Time, hours Fig. 3. The computed hydrographs of runoff to virtual dams on river 1 - Q1(t), on river 2 Q2(t); and the transformable hydrographs by dam 1- q1(t) and by dam 2- q2(t). The forms of the transformable hydrographs depend on sizes of dam spillways and place of their location on the river which can be changed. The modeled hydrograph of runoff to water reservoir transformed to hydrograph after dam in lower reach with help of method of approximate integration of Potapov [3]. The method uses next equations. Qdt qdt dv, (3) 3 q m B 2 g H0, (4) 2 Q water discharge of runoff to water reservoir; q - water discharge in lower reach of water reservoir; V change of water reservoir volume for the time dt; m coefficient of discharge throw spillway; B total width of spillway; H 0 water height over crest of spillway; The resulting hydrograph is obtained by summing the two transformed hydrographs (fig. 4).

5 Le Hong Nhung et al. / Procedia Engineering 154 ( 2016 ) Water discharges, cub m/sec Time, hours Fig. 4. The resulting hydrograph. 3. Results The represented approach provide a possibility to consider different variants of the locations of the flood-control reservoirs and corresponding variants of inundation in the city of Da Nang. References [1] DETERMINATION OF DESIGN HYDROLOGICAL PERFORMANCE Moscow, 2003, P. 70 (Rus). [2] Potapov M.V. Compositions. Vol. 3. Moscow, 1951, P (Rus).