MINISTRY OF EDUCATION & TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATIONS Nguyen Anh Tuan STUDYING THE DETERMINATION OF A NUMBER OF RAIN PARAMETERS TO MAKE CONTRIBUTIONS TO COMPLETING THE FORMULA OF DESIGN FLOW OF SMALL SIZED DRAIN WORKS ON ROAD UNDER THE CLIMATIC CONDITIONS OF VIETNAM Major: Building auto road and city road Code: 62.58.30.01 - 2 - SUMMARY OF DOCTOR OF ENGINEERING Hanoi-2014 PREAMBLE 1. Background for the research. Today, the transportation network has been expanding; urban areas, industrial zones have been developed at a rapid pace. We require a formula to calculate the design flow for simple, easy-to-calculate small drainage structures with the acceptable accuracy. In recent decades, Vietnam has been seriously affected by the climate change phenomenon, increasing the extreme climate phenomena, affecting the rainfall regime in Vietnam. Therefore, it affects the rainfall parameters used in calculating the design flow of drainage works on the road Q p . The use of the research results, previous rainfall data in calculating Q p becomes the reduced reliability, with large errors, giving rise to the damages to works, delaying the transport, increasing costs of repairing and maintaining, affecting the living environment… - 3 - This clearly shows the reality out of the practice, such as the phenomenon of damages to small drainage works on the road due to increasing flood; damages can occur immediately or only a few years after being put into use; phenomenon of water storage at the upstream causes flooding to the fields and villages, affecting the agricultural production often occurs in the Central Region after completing the construction of roads; the phenomena of street inundation after the heavy rains in some urban areas of Vietnam makes difficulties, disturbance for activities and production. . . Obviously, there are outstanding problems, emerged problems of determining the rainfall parameters in formula of calculating Q p of small water drainage works on the roads in Vietnam today. From the above urgent requirements, the dissertation has been selected for the research. 2. Research objectives. - Theoretical research, analysis of nature, proposing principles and methods, formula for determining the parameters of rain used in the formula of calculating design flow of small drainage works on roads under the conditions of Vietnam. - Applying into the practice: immediately, because there has not been enough conditions, targets of determining specific valuation of parameters on rainfall at 12 typically selected meteorological stations, these values are proposed for reference to the practical use in calculating design flow of drainage works on roads in these areas of Vietnam. 3. Research contents. - The thesis focuses on researching and resolving rain parameters. This is the decisive, important and indefinite parameters in calculating Q p of small drainage works on the roads, totally depending on the particular characteristics of the climate in Vietnam. The rainfall parameters of the research are as follows: +) The study shall determine the calculated daily rainfall H n,p at a design frequency tailored to the characteristics of the weather changes in Vietnam. - 4 - +) The study shall identify specific factors of the rain shape Ψ T and issues of rain zoning in line with the requirements on calculating design flow of small drainage works on the roads in Vietnam. +) The study shall determine parameters on the designed rainfall intensity a T,p , corresponding to the concentration time of designed water and design frequency. Calculated rain intensity parameters a T,p is the general impact parameter in calculating design flow of drainage works on the roads. - The above are the parameters on rain used in the formula of calculating design flow of drainage works on the roads. 4. Research methods. Statistical analysis is the main method used in the thesis. 5. Scientific meanings and pratice of the project. - Researching characteristics of rainfall changes, contributing to further elucidate the unusual situation of change of rain in the territory of Vietnam in recent decades. Realizing the urgency to recalibrate or gradually replace the new database of rainfall in line with the weather phenomenon under the affects of the climate changes; suggesting solutions to coping with the phenomenon of radical changes in rain in calculating design flow of water drainage works on the roads in Vietnam today. - The study shall determine the parameters of rainfall (calculated daily rainfall H n, p , calculated rainfall intensity a T,p , logical rain zoning and other characteristics of rain: Ψ T , S p , A, B, m, α) suitable for the climatic conditions in Vietnam used in the formula Q p calculating the small drainage works on the roads. A few researched rain parameters identified in the thesis (such as daily calculated rainfall parameters H n,p , typical characteristic rain shape coefficient Ψ T ) can also be used in the Sokolopsky formula calculating design flow for medium and large basins; used in calculating showers - flow with NAM - MIKE model with reliable results. - 5 - - Rain gauge stations in Vietnam are numerous, but most of them are used to measure daily rainfall and few of them are recording rain gauge stations, so that when the method of directly determining the calculated rain intensity parameters are based on recording rain gauge data, then researching the construction of empirical formula in indirectly calculating the rainfall intensity a T,p in the thesis; issues of transferting the calculated daily rainfall H n,p into the calculated rainfall of each short time H T,p is necessary for calculating the peak flow of the design flood of the basin of drainage works on roads in Vietnam. - To better plan the flood prevention, firstly, it is required to logically zone flood, in accordance with rainfall characteristics of each region. The thesis has researched proposals on criteria, rain zoning methods for mapping the logical rain zoning with a large proportion in accordance with the requirements for calculating flood flow of the small basins of small drainage works on the roads in Vietnam. - The thesis has established the specific parameters of rain, such as calculated daily rainfall H n,p according to the design frequency, typical coefficienmt of the rain shape Ψ T , rain strength S p , factors of the climate zones A, B, coefficient of the rain shape m, the regression coefficient of the climate zone α, standard rainfall intensity a TO,p used in 07 empirical formula that the dissertation researches and develops to calculate the rainfall intensity a T,p corresponding to the concentration time of calculated water and design frequency, for 12 selected typical meteorological stations, including stations at Muong Lay Town-Dien Bien Province, Tuyen Quang City, Lang Son City, Lang-Hanoi, Ha Dong-Hanoi, Son Tay Town-Hanoi, Vinh City, Dong Hoi City, Da Nang City, Nha Trang City, Buon Ma Thuat City, Can Tho City, with the actual rainfall records from 1960 - 2010, reference recommendations forn the practical use to compute the design flow of small drainage works on the roads today in these regions of Vietnam. 6. New contributions of the dissertation. - 6 - - Determining the values of calculated daily rainfall H n,p according to the design frequency at 12 selected meteorological stations on the basis of long actual rainfall recording sequence from 1960 to 2010, in which the last time is supposed to correspond to the new context with the impact of climate change phenomena, applied to calculate the design flow of small drainage works on the roads in accordance with current design standards TCVN9845:2013 [5] or using Sokolopsky formula in computing the design flow for medium and large basins (in the regions located with these meteorological stations). - Determining the values of characteristic coefficient of the rain shape Ψ T for the regions of 12 studied meteorological stations with the rain gauge period from 1960 to 2010, used to calculate the rainfall intensity corresponding to the water concetrating time of the basins and the design frequency used in the standard TCVN9845:2013 [5] to calculate the design flow of small drainage works on the roads. At the same time, it is an important parameter used to calculate the transfer from the calculated daily rainfall H n,p to the calculated rainfall of each short timeH T,p used in Sokolopsky formula to calculate the design flow for medium and large basins in calculating showers-flow with the NAM-MIKE model with the reliable results. Also, the characteristic rain shape coefficient Ψ T can also be used as a criterion for zoning the rain. - Summarizing and researching to improve into 7 types of empirical formula in calculating the calculated rain intensity parameter a T,p corresponding to the water concentration time of the basin and the design frequency used to calculate the design flow of small drainage works on the roads in Vietnam corresponding to the different conditions on rainfall data available in the design areas, in which there are 3 types of new improved formula of the thesis, the formula remains the coefficients in the formula new building for the thesis area 12 meteorological stations selected for the study period rainfall in 1960-2010. - 7 - Chapter 1: OVERVIEW ABOUT THE RESEARCH ISSUES 1.1. Domestic and international related researches. 1.1.1. Theoretical basis of the formula for determining the maximum flood current flow due to rain on the catchment [32]. - The formula of the limited intensity determining the design flood peak flow is drawn from the famous flow formula whose basis is the theory of concentrating water from the basin. This theory was firstly analyzed and researched by USSR scientists (N.E. Dongov, M.E. Velikanov and M.M.Protodiakonov) and it is now widely used in the world in the field of hydrological computation. The assumptions are. +) Basins are evenly shaped, the river bed in the middle. +) Rain and losses are evenly distributed over the entire basin and with unchanged intensity during the computation time. +) Considering the rain frequency of flood flow to be equal to the flood flow frequency. - By analyzing rules of water running from slopes of the basin to drainage works, the authors of the theory of concentrating water from the basin have drawn the formula for determining the maximum flow of the design flood flow. FaKQ pp , τ ϕ = (1.1) In which: Q p is the design flow at frequency p; F is the catchment area ϕ is the flow coefficient with regard to the amount of lost rain water a τ ,p is calculated rainfall intensity at water concentration time τ of the basin and the frequency p. It is the max average rainfall intensity during the water concentration time τ and frequency p - 8 - K is the unit conversion coefficient when elements in the formula are not calculated at the same unit. K = 16.67 when Q p is in m 3 /s, a τ ,p calculated in mm/ph, F in km 2 . - Formula (1.1) is the basic formula. From the basic formula (1.1), very many authors have studied the application and completed to suit the actual conditions in terms of rainfall intensity distribution law, water running conditions on the natural basins. 1.1.2. Formula defining the design flow for small drainage works on the roads in some countries and in Vietnam. 1.1.2.1. In some countries: countries with the developed science such as the U.K., the U.S., Russia, Japan, China, etc use the limited intensity formular in the form (1.1) to determine the design flow Q p for small water drainage works on the roads. 1.1.2.2. The formula for determining the design flow for small drainage works on the roads in Vietnam - The formula of the limited intensity of the standard TCVN9845:2013: Calculation of flood flow characteristics [5]: applied to the basin with F ≤ 100 km 2 . 1, δϕ FHAQ pnpp = (1.9) In which: A p is the relative flood peak flow module at the frequency p A p = 16.67Ψ τ / τ H n,p is the calculated daily rainfall at the frequency p δ 1 is the factor with regard to effects of ponds, lakes, and swamps. - Limited intensity formula of National University of Civil Engineering (the formula proposed by Prof., Dr.Nguyen Xuan Truc) [3], [32]. - 9 - The small drainage structures on roads in Vietnam often have the small catchment area (usually less than 1 km 2 to a few km 2 ), so the water concentration time τ is short. Therefore, the calculation of Q p is based on the rain intensity parameters with the short calculation time, but the high rain intensity will be more accurate than using the daily rainfall parameters as in the formula (1.9) of the design standard [5]. With that viewpoint, since the 1980s, Prof. Dr. Nguyen Xuan Truc has proposed using the following formula (1.10) to calculate the design flow Q p for small drainage structures on roads with the basin area F≤30 km 2 in Vietnam. 1, 67.16 δφϕ τ FaQ pp = (1.10) With: φ the flow reduction coefficient depending on the basin area. - Limited intensity formula used in calculating urban road drainage under the design standard TCVN7957:2008 [8]. FqCQ pp , τ = (1.11) With: C is the flow coefficient, depending on the nature of the basin surface and p q τ ,p is the rain flow module or rain intensity according to the calculated volume corresponding to the water concentration time τ and design frequency p q τ ,p = 166.67a τ ,p In which: q τ ,p in liter/s/ha, a τ ,p in mm/ph. 1.1.2.3. Sokolopsky Formula [3], [15], [32]. This is the kind of volume formula used to calculate the flow of water drainage works on the roads with the basin area F>100 km 2 . - 10 - 0 0, )(278.0 QFf t HH Q l p p + − = δϕ τ (1.12) With: H τ ,p is the calculated rain flow at the water concentration flow τ of the basin and the frequency p. It is the max rainfall during the water concentration time τ and the frequency p (mm) H 0 is the initial lost rain water (mm) f is the factor of flood shape , t l the duration of rise (h) δ is the coefficient with regard to the influence of reduced flow of ponds, swamps and forests in the basin Q 0 the water flow in the river before the flood (m 3 /s). 1.1.3. The problem of determining the parameters in the formula for calculating the design flow of small drainage works on the roads. The parameters of rain in the formula for calculating the design flow of small drainage works on the roads are: calculated daily rainfall H n,p at the design frequency p; characteristic rain shape coefficient Ψ T and the issue of rain zoning; the calculated rain intensity a τ ,p at the water concentration time τ and design frequency p. 1.1.3.1. Calculated daily rainfall H n,p . - Calculated daily rainfall H n,p is determined by the statistical analysis method on the basis of sequence of data measuring actual daily rainfall for many continuous years at rain gauge stations within the project design area. - Up to now, the fullest database about H n,p in Vietnam was founded in 1987 in accordance with the design standard TCVN9845:2013 [5], for 589 points of rainfall gauge across the country with the frequency p=1%, 2%, 4%, 10%, 25%, 50%. Since then now, it has passed over 25 years, the rainfall regime in Vietnam has been changed, influenced by the phenomenon of climate change, so the database has become less accurate so far. 1.1.3.2. Characteristic coefficient of the rain shape Ψ Τ and rain zoning. [...]... changes in Vietnam to be used in calculating Qp of drainage works on the roads max Lấy mẫu và kiểm calculated daily rainfall H ngày lớn the năm H frequency p 3.1.2 Defining theđịnh mẫu thống kê lượng mưa n,p undernhất designngày thu thập thực tế Kiểm tra tính đại biểu: / Kiểm tra sai số lấy mẫu / Kiểm tra thời kỳ lấy mẫu Tính tần suất kinh nghiệm: / Công thức kỳ vọng Xử lý mưa đặc biệt lớn Tìm đường tần... - Menkel (K-M) / Vẽ tìm đường tần suất lý luận phù hợp theo phương pháp đường thích hợp Kiểm định sự phù hợp của đường tần suất lý luận với tài liệu thực đo: / Sử dụng tiêu chuẩn kiểm định Smirnov - Kolmogorov - 29 - Figure 3.1: Chart determining the calculated daily rainfall Hn,p with the statistical analysis of daily rain measurement sequence at rain gauge stations in Vietnam, often continuous 3.1.3... WORKS ON THE ROADS - 16 2.1 Overview of Vietnam climatic conditions - Vietnam is within the humid tropical, monsoon climate The annual rainfall and rain duration are relatively large, averaging from 1100 - 8000 mm/year and from 67-223 days of rain/year, compared with countries in the same latitude, it is about 2.4 times higher [25] - The rainfall regime in Vietnam is under the effect of three main factors:... parameters for calculating the design flow of small drainage works on the roads, reflecting more closely the condition climate and terrain of Vietnam It is necessary to research and determine the calculated rain intensity parameter a T,p under the climatic conditions of Vietnam used to determine the design flow of small drainage works on the roads Q p in order to ensure the required level of precision Chapter... the rain; buffering surface factors; effects of socio-economic activities of human beings +) Under the climatic conditions of Vietnam, the rain is a factor directly affecting the flood flow of small basins and the rain is the cause of flood flows on small watersheds in Vietnam +) Buffering surface factors including: geographical location, topographical and geomorphological features, geological and soil... historical circumstances, continuous and reliable monitoring data are from the year 1980 now - In the thesis, rain gauge data is collected from 1960 - 2010 (stations in the North Vietnam), from 1980 to 2010 (stations in the South Vietnam) The sequence of research data is 30-50 years long, so results ensures the necessary reliability - 17 2.3 Studying rainfall variability features under the effect of the phenomenon... small drainage works on the roads in Vietnam today is the determination of the rain parameters in formulars calculating Qp of small drainage works on the roads Because the currently used parameters were set in previous, they are not matched with the computational requirements Q p of small drainage works on the roads in the weather and climate conditions in Vietnam today - Zoning rain (too wide and for... present conditions in Vietnam and it is necessary to propose the researches for correcting - The calculated rain intensity parameters are of the general and representative characteristics for the rain regime and the shape of the rain zone, for the specific watershed buffering surface, the water concentration time and design frequency, it is characterized by the distinct climates of Vietnam, so it is necessary... of rain to the present time in Vietnam - At the same time, the coefficient ΨT was used to determine the highest rainfall in periods calculated H T,p at a frequency from Hn,p according to frequency, HT,p = ΨT.Hn,p , used in the flow calculation formula Sokolopsky designed for medium and large basins, it is also important parameters in calculating showers-flows with NAMMIKE model with reliable results... the U.S., India, Russia, China, Japan, Korea China, Indonesia, Malaysia, etc In these formulas, compared to above basic formulations, they can be added or subtracted a few regression coefficients In Vietnam, there have been many studies to suit the climatic conditions of the nation, typically: / The research of Prof., Dr Nguyen Xuan Truc in the year 1980 for 18 meteorological stations: A + B lg N aT , . In recent decades, Vietnam has been seriously affected by the climate change phenomenon, increasing the extreme climate phenomena, affecting the rainfall regime in Vietnam. Therefore, it affects. and large basins; used in calculating showers - flow with NAM - MIKE model with reliable results. - 5 - - Rain gauge stations in Vietnam are numerous, but most of them are used to measure daily. climatic conditions of Vietnam, the rain is a factor directly affecting the flood flow of small basins and the rain is the cause of flood flows on small watersheds in Vietnam. +) Buffering surface