Water drainage

Darcy’s lawGroundwater flow

Design water drainage Pipelines

1

Flow through a dike

Seepage (kwel) flows through dam

Pressure line

1

Piping erosion

Water pressure

Seepage (kwel) beneath structure

civil structure

Flushing of particles

1

Dewatering (verlagen grondwaterstand)

Maximum capacitity

Well point system

Size filters

Original ground water level

1

Groundwater level

New groundwater level because of rain

percipitation Ditch or drainage

Drainage

2

Landuse / Grondgebruik Percipitation

Neerslag (mm/dag)

Groundwater level below surface

Grondwaterstandsdiepte (m)

grassland / grasland 7 (10) 0,30 (0,20)

farm land / bouwland 7 (10) 0,50 (0,30)

horticulture / vollegronds tuinbouw 7 (10) 0,50 (0,30)flower bulbs on clay soil / bloembollen op klei 7 0,50flower bulbs on sand soil / bloembollen op zand 10 0,30

fruit / fruitteelt 7 (10) 0,70 (0,60)

forest / bos 5-7 0,50 - 0,30

military training area / militair oefenterrein 7 0,70athletic fields, camping areas, play grounds /sportvelden, kampeerterreinen, speel- en ligweiden 15 0,50

building sites / bouwterreinen 10 0,50

urban area / woongebieden (50% verhard) 5 0,70

industrial area / industrieterreinen 7 0,50 2

3

Groundwater flow

Darcy’s law

3

3

Soil / grondsoort

conductivitydoorlatendheid

(m/day)heavy clay /zware klei 0.0001potklei 0.001Moderate heavy clay / matig zware klei 0.01sandy clay / zandige klei 0,05bolder clay / keileem 0,05peat / veen 0.001 - 0.1clay peat / kleiig veen 0,005sandy peat / sterk zandig veen 0,05loam /leem/löss 0,05sandy loam / zandige leem 0,3silt / lichte zavel 0,5humus / teelaarde 5shells / schelpen 30fine sand / fijn zand 1 - 10dune sand / duinzand 7coarse sand / grof zand 30very coarse sand / zeer grof zand 80

very coarse sand / uiterst grof zand 200fine gravel / fijn grind 1.000 - 10.000coarse gravel / grof grind 10.000 - 100.000

Darcy’s law

IAkq Ikv

Laminar flow

q = discharge [m3/s]k = hydraulic conductivity [m/s]A = area [m2]I = S = slope pressure line

3

]1[ Redv

w

If Rew < 5 Laminar flow

Rew = Reynolds number [1]

v = Average velocity [m/s]

d = Average grain size [m]

ν = Kinematic viscosity [m2/s] = 10 -6

3

Reynolds number

Groundwater level rise

New groundwater level because of rain

percipitation Ditch or drainage

Drainage

4

Drainage agriculture parcel

22

max/ amiddle HKaWH

4

HaHmiddle/max

W

a

K

Drainage agriculture parcel

22

max/ amiddle HKaWH

W = vertical velocity rainfall [m/s]a = horizontal distance from stream channel to highest ground water level [m]K = hydraulic conductivity [m/s]Ha = vertical distance from impereable layer to water level stream channel [m]Hmiddle= vertical distance from impereable layer to highest ground water level[m]4

Design criteria drainage pipeline• Manning’s formula• n=0,013 s/m1/3

• Sbed =1/1000• Pipe 50% filled with water• Outflow 10 cm above surface water

u = mean velocity [m/s]R = hydraulic radius [m]S = slope energy line [1] assumed is that Sf = Sbed

n = manning’s roughness coefficient [s/m1/3]nSRu

21

32

5

m 4

4/1 2 DDD

OAR

m 4)(5,0

)4/1(5,0 2 DDD

OAR

R and circle’s

5