Trench

Mulden infiltration system in the EXPO settlement on Kronsberg in Hanover

A trench is an underground, rarely also partially above-ground buffer storage, in order to absorb and drain away rainwater . For this purpose, a trench is filled with gravel or other graded materials that are protected against contact erosion.

Structure and suitability

Infiltration structures are characterized by a good retention effect and, due to their underground location, they require little space. However, they are not serviceable and are subject to the possibility of clogging. A sand trap (including solids collector) should therefore be installed in front of the feed line into the trench to prevent dirt , stones , gravel and similar materials from being deposited in the trench pores. In the long term, an entry would lead to the infill of the infiltration system with impermeable material and this would then no longer offer proper rainwater infiltration. Underground pipe trenches or trench cuboids can easily be built under paved paths and drivable areas.

Dimensioning

${\displaystyle Qs=(b+0{,}5h)\cdot L\cdot 0{,}5K_{f}}$ in m³ / s

${\displaystyle {\boldsymbol {Qs}}}$ = Percolating volume flow in m³ / s

${\displaystyle {\boldsymbol {b}}}$= Width of the bottom of the trench in m

${\displaystyle {\boldsymbol {h}}}$ = usable height in m

${\displaystyle {\boldsymbol {L}}}$ = Length in m

${\displaystyle {\boldsymbol {K_{f}}}}$= Permeability coefficient in m / s (e.g. approx. 0.0001 m / s for sand)

See also

• Trench → deep plowing

Web links

Wiktionary: Rigole  - explanations of meanings, word origins, synonyms, translations

• Diagram of a trench