DIAGNOSTIC AND ASSESSMENT OF A URBAN BASIN SEWER SYSTEM at Riereta, Sant Boi de Llobregat, SPAIN

1. Presentation Nº 1: “HYDRO LATIN AMERICA 2011” Cochabamba. July 2011 DIAGNOSTIC AND ASSESSMENT OF A URBAN BASIN SEWER SYSTEM at Riereta, Sant Boi de Llobregat, SPAIN AVANCE REPORT

2. STUDY AREA DESCRIPTION AND LOCALIZATION Sant Boi de Llobregat is located in the metropolitan area of Barcelona, ​​in Barcelona province, Cataluña. It has 82,428 inhabitants (INE 2009) and it occupies an area of ​​22 km2. The analysis area ​​in this study is the urban watershed of La Riereta, located at old municipality of Sant Boi de Llobregat. It has an area of ​​approximately 15.5 ha.

3. STUDY AREA DESCRIPTION AND LOCALIZATION At the standpoint of urban drainage, one of the main features of the basin is its high rate of impermeabilization which causes a significant increase on stormwater runoff. Current state of sewerage system, concerning ducts sizes and antiquity, aggravates this problems. • 1 – Increasing in volume • 2 – Flow accelaration • 3 – Runoff peak increasing

4. OBJETIVES General Objetive Hydrological and hydraulic behavior evaluating and diagnosing of an existing sewerage network in Riereta region, Sant Boi de Llobregat, through the use of EPA SWMM computer program. • Determine in a given year, the probability of overcapacity occurrence in the network, to a certain series of precipitation; • Determine flooding volumes in the study area for that series; • Determine peak flow rates registered during the series; • Estimate flooding permanence during this period; • Determine vulnerable areas of flooding-related phenomena in the study area; • Assess safety level in existing sewer system for a given time of recurrence (TR), identifying maximum TR which do not have surface flooding occurrence and existing network works with free surface. Particular Objetive

5. METHODOLOGICAL USED PROCESS Based on available information Definition of basins and urban sub-basins Topographic information of the region Existing network sewerage Urban parcelling layout • Satellite images support: • Characterization of impervious areas. • Discharge form of roofs and buildings.

6. METHODOLOGICAL USED PROCESS SUB-BASIN: Definition of hydrological characteristics parameters LINKS: Definition of hydraulic characteristics parameters Construction of drainage topological scheme P R O C E S S Analysis of meteorological events - Construction of design rainfall. Determination of effective hyetographs to estimate runoff, regarding that runoff losses (PL) are constant. It can speed up the calibration process. Valid assumption for urban watersheds due to its fast response time. Calibration and validation of model based on available hydrological information. Chosen events were Jordi, Fidel and Martina, recorded in the basin study. Diagnosis of drainage system considering a design rainfall with 10 years TR and duration of one hour. Fulfill the objectives for Team No. 4.

7. METHODOLOGICAL USED PROCESS GANT DIAGRAM

8. SHORT WATERSHED CHARACTERIZATION • Riereta basin is located in the old town of Sant Boi de Llobregat, in the metropolitan area of ​​Barcelona. • The study basin is a urban type basin and has an area of ​​about 15.5 ha. • It presents high impermeabilization levels and it is completely urbanized. The houses are old. • The terrain is extremely rugged with slopes ranging between 4% and 0.5%. • Some of the distinctive characteristics of sewer system are: • Combined sewer system; • Concrete ducts with mostly circular sections and diameters ranging between 300 mm and 1200 mm; • Linking ducts through concrete inspection chambers;

9. SHORT WATERSHED CHARACTERIZATION Satelyte image with basin delimitation. It can be viewed the high impermeabilzation hate 18 Subbasins 0.65 – 1.25 ha

10. NETWORK SYSTEM

11. HYDROLOGICAL PARAMETERS DETERMINATION CHARACTERISTIC WIDTH “W”: Given that real basins are not rectangular neither have symmetric and uniform properties, it is necessary to adopt a process that permit to estimate characteristic width to general situations. Sk = (A2 – A1) / A  W = (2 – Sk) * l Sk = Correction factor; 0 ≤ Sk ≤ 1 A1 = Area at one side of drainage channel A2 = Area at other side of drainage channel A = Total area l = Lenght of main drainage channel

12. HYDROLOGICAL PARAMETERS DETERMINATION S U B - B A S I N S

13. HYDRAULIC PARAMETERS DETERMINATION C O N D U C T S

17. SWMM MODEL SCHEME

18. CALIBRATION OF MODEL • It is necessary to identify the parameters to be considered for calibration. It is known to use the MPLC with which values ​​are not required pervious area (assuming the entire area impervious), second volume in depression will not be necessary. On that basis, the parameters used for the iterative process are: • Loss constant in mm / h [Pl] • Characteristic width in m [W] • "n" Impervious surface area Manning, • "n" Manning duct of the sewer system. • The calibration is carried out with the event Fidel and validated for the events Martina and Jordi. ?

19. Presentación Nº 1: “HYDRO LATIN AMERICA 2011” Cochabamba. Julio de 2011 DIAGNOSTIC AND ASSESSMENT OF A URBAN BASIN SEWER SYSTEM at Riereta, Sant Boi de Llobregat, SPAIN AVANCE REPORT