sistemas de drenagem de Águas pluviais (detention … · du - 52 sistemas de drenagem de Águas...

DU - 50

SISTEMAS DE DRENAGEM DE ÁGUAS PLUVIAIS

BACIAS DE RETENÇÃO (Detention ponds)

ADVANTAGES

• Cost

• Expansion flexibility

Objectivos – ART. 176º

• reduction flood risks

• creation leisure areas (for fishing e boating…)

• making water store areas (agriculture, fire fighting, industries, municipal street washing,

parks irrigation …)

• Environmental protection (reduction of suspended solids and organic mater)

Bacias (detention ponds)

DU - 51



DU - 52


• regarding the implanting - ponds in open air dry areas

permanent water level

- burried ponds (storm tanks)

Permanent water level or dry ponds? It depends from:

• objectives (water quality, recreational,…)

• water level and and sazonal flutuations of underlying aquifer

• permeability

• financial availability

Dry Ponds lower financial and construction requirements

do not require high water levels ("constant feed")

Tipos – ART. 177º

• regarding the location - ponds in series (“online” e “offline”)

- ponds in parallel

(relativaly to the arriving sewer or channel)


DU - 53


Constituição – ART. 178º

• Pond main body bottom and earth verge

covered embankments with vegetation cover (landscaping)

• Dischage devices Bottom discharge

Work head and output

Sewer

• Safety Devices Surface discharge

Detention pond deployment)

• take advantage area with natural depression;

• At the work head of the detention pond construct a concrete chamber (to avoid

damages in pipe bed and / or clogging with dirt and other sediments)

• trace transverse and longitudinal profiles to build the curve of volumes stored (calculate

volume of stored water for different water levels)

• check that the high water level allowed ensures the sizing volume that is needed.


DU - 54


Aspectos construtivos – ART. 180º

Bacia a seco (dry detention ponds)

• Bottom slope 5/100 (prevent the formation of quasi-permanent wet areas);

• Maximum slopes of embankments of 1/6 ou 1/2

(respectively for public access or not).


DU - 55


Ponds with permanent water level:

• Minimum water level of 1,5 m (avoid excessivo aquatic plants development and

ensure any fish life)

• ensure appropriate treatment of verges (embankments lawns, etc ...)


DU - 56


Water Quality

Improve water quality of stormwater received

Occur transformations of physical, chemical and microbiological

• Sedimentation of suspended soils reduction of water turbidity

• Variation of DO of the water body balance between “inputs” (rearation and

fotosinthesis) and consumption

• variation of the nutrients (N, P) plants behaviour and impacts

• Reduction of microrganisms solar radiation, biologic competion,

temperature e sedimentation

Typical impact:


DU - 57


Simplified Method (ABREU, 1983) or Dutch method

• Based on the knowledge of the IDF curves of rainfall in the area under study

• Lets you calculate the volume required to store the resulting tributary flow of critical rainfall,

for T return period, to ensure a constant flow q, corresponding to the maximum flow

capacity of the downstream drainage structure.

• Expeditious Method suitable for the preliminary design of the retention basin.

• Data: A, C of the catchment

IDF curve parameters

Efluente flow q (constant) non conservative procedure

Hydraulic design – ART. 179º

• Objective: find the volume design needed to have efluent flow similar to the natural

catchment (AI = 0 %)

• T = 10 a 50 anos (usually)


DU - 58



DU - 59


PULS Method

• Is based on the numerical resolution of the volumes conservation or the continuity equation

applied to the retention basin.

• Solves the most complex situations (ex .: discharged flow variable with time or water level in the

pond)

• Data: Input flow hidrogram

Discharge low of output flow

Storing law (Volume vs water level)

tQQ

tQQ ididiaia

ihihse22

1,,1,,

,1,

1,1,,,1,, 22 ihidihidiaia QtQQQ

logo

Known Terms Function of h(i+1), the only unknown variable


DU - 60



𝒊 =𝒂

(𝑻𝑫 + 𝒃)𝑪

𝑸𝑷 = 𝑪 𝒊 𝑨

Peak discharge rate:

Inflow hydrograph volume:

Precipitation Intensity:

𝑽𝒊 = 𝟔𝟎 𝟎, 𝟓 𝑸𝑷 𝑻𝑫 − 𝒕𝒄 + 𝑻𝑫 + 𝒕𝒄

Outflow hydrograph volume:

Detention storage volume :

𝑽𝒐 = 𝟔𝟎 𝟎, 𝟓 𝑸𝑨 𝑻𝑫 + 𝒕𝒄

𝑽𝒔 = 𝑽𝒊−𝑽𝒐= 𝟔𝟎 𝑸𝑷𝑻𝑫 − 𝟑𝟎𝑸𝑨 𝑻𝑫 + 𝒕𝒄

The rainfall duration TD for maximum retention volume is

determined by differentiating Vs with respect to TD:

𝑻𝑫 𝟏 − 𝒄 + 𝒃

𝑻𝑫 + 𝒃 (𝒄+𝟏)−

𝑸𝑨

𝟐𝑪𝑨= 𝟎

DU - 61


INFILTRATION CHAMBERS

Purpose

• store and infiltration of stormwater;

economic solution and effective, suitable for permeable soil areas;

Kinds of systems

DU - 62


Infiltration

Chambers

Capacity (factors that depends):

• size of the the basin to drain;

• rainfall characteristics of the zone;

• degree of soil permeability;

• average slope of the basin drained;

• hydraulic conductivity of the soil.

Desadvantages

• not suitable for clay, silty or sandy-silty soils

• risk of contamination of aquifers caused by mixing of wastewater with rainwater

• high costs associated with the maintenance and operation (regular cleaning)

• high difficulty of rehabilitation

percolated water flow increases with the water level increase inside the

chambers (in the absence of soil sealing).

DU - 63


Construction:

• precast rings

• carefully constructed

Percolations by the bottom

infiltrations by joints, and between rings

• Shoud be easily accessed

Located in the field in areas with:

similar elevations

Pipe links between chambers:

Minimal slope 1/D

(ensure self-cleaning)

placed in levels to ensure the

mobilization of the total capacity of the

drainage chambers

Infiltration

Chambers

DU - 64


Hydraulic design

Assumptions considered:

• linearity between the hydraulic load on the bottom of the chamber and the flow

percolated;

• application of generalized rational method for determining the maximum flow rate (for a

given T);

• constant influent flow to each chamber during the critical precipitation and its precipitation

intensity;

• complete filling of the chamber, on the occurrence of the critical precipitation

Expressões de cálculo (ESCRITT, 1947)

Infiltration

Chambers

DU - 65


Metodologia de cálculo

Infiltration

Chambers

SWMM is a distributed, dynamic rainfall-runoff simulation

model used for single event or long-term (continuous) simulation

of runoff quantity and quality from primarily urban areas.

• The runoff component of

SWMM operates on a collection

of subcatchment areas that

receive precipitation and

generate runoff and pollutant

loads.

• The routing portion of SWMM

transports this runoff through a

system of pipes, channels,

storage/treatment devices,

pumps, and regulators.

DU - 66

Introduction to USEPA SWMM

67

Typical Applications of SWMM

Design and sizing of drainage system components

including detention facilities

Flood plain mapping of natural channel systems

Control of combined and sanitary sewer overflows

Generating non-point source pollutant loadings for

wasteload allocation studies

Evaluating BMPs and LIDs for sustainability goals

68

Limitations of SWMM

Not applicable to large-scale, non-urban watersheds

Not applicable to forested areas or irrigated cropland

Cannot be used with highly aggregated (e.g., daily) rainfall data

Its an analysis tool, not an automated design tool

Processes Modeled by SWMM

DU - 69

SWMM Chronology

1971 - SWMM I (M&E, UF, WRE)

1975 - SWMM II (UF)

1981 - SWMM 3 (UF & CDM)

1983 - SWMM 3.3 (PC Version)

1988 - SWMM 4 (UF & CDM)

2005 – SWMM 5 (EPA & CDM)

DU - 70

Hydrologic Modeling Features

Hydrologic features:

• Spatially and time varying rainfall

• Evaporation of standing surface water

• Snow accumulation and melting

• Interception from depression storage

• Infiltration into soil layers

• Percolation into shallow groundwater

• Interflow between groundwater & channels

• Nonlinear routing of overland flow

The spatial variation is obtained by the prior definition of smaller subcatchments of the

study area, homogeneous in terms of their physical characteristics.

DU - 71

Hydraulic Modelling Features Hydraulic features:

• Handles drainage networks of any size

• Accommodates various conduit shapes as well

as irregular natural channels

• Models pumps, regulators, storage units

• Allows external inflows from runoff,

groundwater, RDII, sanitary, DWF, and user-

supplied time series

• Uses flexible rule-based controls for pumps

and regulators

• Models various flow regimes, such as

backwater, surcharging, reverse flow, and

surface ponding

DU - 72

Water Quality Modelling Features Water Quality features:

• Pollutant buildup over different land uses

• Pollutant washoff during runoff events

• Reduction in buildup from street cleaning

• Reduction in washoff from BMPs

• Inflows from user-defined sources and sanitary DWF

• WQ routing through the drainage network

• User-defined treatment functions

Graphic representation:

• GIS interface and the possibility of integration of coordinated plants

• Colour representation in plan and profile simulation over time

• Statistical analyses DU - 73

Chap 1 – Introduction

Chap 2 – Quick start tutorial

Chap 3 – SWMM´s conceptual model

Chap 4 – SWMM´s main window

Chap 5 - Working with Objects

Chap 6 – Working with Projects

Chap 7 – Working with the map

Chap 8 – Running a simulation

Chap 9 – Vieweing Results

Chap 10 – Printing and copying

Chap 11 – Files used by SWMM

Chap 12 – Using add-in tools

Apendix: A – Usefull tables

B – Visual object properties

C – Specialized properties editors

D – Command line SWMM

E – Error and warning messages

SWMM Manual

Very usefull for

quick start

Very usefull

to be consulted

DU - 74

Conceptualization model

Atmosphere

compartment

Land surface

compartment

Groundwater

compartment

Transport

compartment

Raingage objects: rainfall inputs

Subcathment objects

Node and link objects Aquifer objects

Precipitation falls / snow

Pollutants

Infiltration

Surface runoff

Pollutant loadings

Groundwater

interflow

Dry weather inflow

User defined hidrographs

DU - 75

76

SWMM 5’s Visual Objects

Data categories Glossário:

Afluências de caudal: inflows

Área impermeável: impervious area

Área permeável: pervious area

Armazenamento superficial: depression storage

Bombas: Pumps

Caixas de visita: Junctions

Colectores: Conduits

Cota de soleira: invert elevation

Descarregador: weir

Escoamento em tempo seco: dry weather runoff

Escoamento em tempo chuvoso: wet weather runoff

Largura: Width

Inclinação: slope

Infiltração:infiltration

Maré: tide

Modelo de escoamento: Routing model

Nós: Nodes

Regras de funcionamento: control rules

Saída de resultados: Reporting

Secção transversal: transects

ST: Profundidade do nó: Node max depth

Subbacias :Subcathments

Troços: Links

Udómetros : Rain Gages

Unidades de caudal: flow units DU - 77

Data categories

Visual objects

udómetros,(Rain Gages)

bacias de drenagem, (Subcatchments)

nós, (Nodes)

troços, (conduits)

Reservatórios (storage units)

Non-visual objects

climatologia (T, evaporação, vento, etc),

neve,

aquíferos,

hidrogramas,

secções transversais,

afluências de caudal,

poluentes,

utilizações de solo,

tratamento de águas residuais,

curvas (de bombas, de maré, etc),

séries temporais (de precipitação, etc)

padrões temporais (de DWF, etc)

DU - 78

Cross section for conduits

DU - 79

Computational Methods

Surface Flow

Subcatchements Non linears storm tanks Evap P, snow

d

dP – dep storage

Q Q When d > dP

Q: Manning equation

Infiltration

Horton Equation

Necessário: taxas de infiltração máximas e mínimas, coeficiente de decaimento, tempo que demora o solo

saturado a secar

Green-Ampt Green-Ampt

Necessério: humidade inicial, conductividade hidráulica do solo, carga hidráulica na frente molhada

SCS Method (Curve Number)

Need to know the soil ocupation

DU - 80

Escoamento no subsolo (Groundwater)

Assume that the surface area of the ground is not

saturated with a given moisture content and the

deeper zone is saturated

Registam-se diversos fluxos

volume /(área.tempo)

DU - 81

Computational Methods

82

Flow Routing Algorithms in SWMM5

Steady Flow simple hydrograph translation applicable only to branched networks

Kinematic Wave gravity force balanced by friction force attenuated & delayed outflow due to channel

storage applicable only to branched networks

Dynamic Wave solves full St. Venant eqns. accounts for channel storage, backwater effects,

pressurized flow, and reverse flow applicable to any network layout requires smaller time step

83

Steady Flow Routing

Actually just sums instantaneous subcatchment runoff for all subcatchments upstream of the selected channel

Kinematic Wave

Uniform, unsteady flow

No backwater, no surcharge, tree branch systems only unless flow splits are input

Dynamic Wave

Non-uniform, unsteady flow

Backwater, surcharge, looped or parallel sewers, street routing of flooded sewer manholes

Flow Routing Algorithms in SWMM5

84

General Conceptual Model for Dynamic Wave

85

Link and Node Properties

86

Hydraulic Boundary Condition at Nodes

JN

JN+1

Grelev(NN,1)

Grelev(NN,2)

87

Node Flooding Options

88

Surface Routing of Flood Flows

JN

JN+1

Zp(NN,1)

Zp(NN,2)

Métodos computacionais

Flow in the sewer system

Escoamento em pressão: Preissmann’s Slot approach

Necessário atentar ao passo de cálculo

Numerical Method: Picard iterations (explicit method) and variable time step dependent of Courant

stabilit condition

DU - 89

Simulation Necessário pré-definir uma série de opções

Geral: unidades, modelo de infiltração, modelo

hidráulico, se permite alagamento e se se pretende

relatório sobre as acções de controlo

Datas: início e fim da simulação, início da saída de

resultados, início e fim da limpeza de ruas (para estudos

de qualidade), período seco anterior

DU - 90

Simulation

Intervalos de tempo: escoamento em tempo de chuva

e em tempo seco, modelo hidrodinâmico e saída de

resultados; a verificar se ocorrerem erros na simulação

Ficheiros: referencia os ficheiros externos que se

pretende utilizar: de P, runoff, RDII, hotstart (usar os

resultados de outra simulação como condições de inicio para a presente

simulação)

DU - 91

Simulation Onda dinâmica: é possível optar por critérios

diferentes para a resolução numérica das equações

com vista a reduzir a probabilidade de erro e

instabilidade

Inertial Terms:

Indica o que fazer com os termos inerciais da equação da conservação

de massa de St. Venant

KEEP: mantém estes termos em qualquer condição

DAMPEN: reduz esses termos à medida que o escoamento se aproxima

de crítico e ignora-os quando o escoamento é rápido

IGNORE: retira esses termos da equação, produzindo uma solução de

onda difusiva (esta solução minimiza a probabilidade de instabilidade)

Variable time step: Usado para satisfazer a condição de estabilidade de

Courant e para prevenir uma variação excessiva de altura de água em

cada nó

Safety factor: Entre 10% e 200%, aplicável ao Dt variável calculado pelo

critério de Courant (quanto menor, menor a probabilidade de instabilidade)

Time step for conduit lengthning: Artifício usado para aumentar o

comprimento de colectores por forma a que se cumpra a condição de

Courant em secção cheia (ou seja, de modo a que o tempo de percurso

de uma onda não seja inferior a este tiem step) Quanto menor este valor,

menos troços irão reqerer ser aumentados.

Minumum surface area: valor mínimo a considerar nos nós quando se

simula alterações em altura de água

DU - 92

94

Homework

1. Download SWMM5 from the EPA Website

http://www.epa.gov/ednnrmrl/models/swmm/index.htm

2. Download the User’s Manual

3. Page through the Users Manual so you are

familiar with it

4. Look at the tutorial and be prepared to run

it in class

http://www.epa.gov/ednnrmrl/models/swmm/index.htm

sistemas de drenagem de Águas pluviais (detention … · du - 52 sistemas de drenagem de Águas...

Documents