7. Rainfall-runoff relations#
Fig. 7.1 Performing discharge measurements during Fieldwork in Luxembourg – photo by (Neijenhuis, 2023).#
Nomenclature
Symbol |
Quantity |
Quantity name in Dutch |
Dimension |
Widely used unit (if not SI) |
|---|---|---|---|---|
\(A\) |
Area |
Oppervlakte |
[L\(^2\)] |
|
\(A_c\) |
Cross-sectional area (of a watercourse) |
Doorsnede (van een rivier) |
[L\(^2\)] |
|
\(b\) |
Channel width |
Beddingbreedte |
[L] |
|
\(C\) |
Runoff coefficient to reflect the ratio of surface runoff to rainfall |
Afvoercoëfficient om de verhouding tussen oppervlakteafvoer en regenval weer te geven |
[-] |
|
\(C_f\) |
Runoff coefficient adjustment factor to account for reduction of infiltration and other losses during high intensity storms |
Aanpassingsfactor voor afvoercoëfficiënt om rekening te houden met vermindering van infiltratie en andere verliezen tijdens stormen met hoge intensiteit. |
[-] |
|
\(C_r\) |
Reduction coefficient accounting for losses |
Reductiecoëfficiënt welke rekening houdt met verliezen |
[-] |
|
\(C_z\) |
Chézy roughness coefficient |
Coëfficient van Chézy |
[L\(^{1/2}\)/T] |
|
\(E_i\) |
Interception |
Interceptie |
[L/T] |
|
\(h\) |
Water level (also: water depth) |
Waterstand (ook: Peil) |
[L] |
|
\(I\) |
Infiltration |
Infiltratie |
[L/T] |
|
\(i\) |
Rank in descending order (Used in Section 7.2.4.3) |
Rang in aflopende volgorde |
[-] |
|
\(i\) |
Rainfall intensity (Used in Section 7.3.3) |
Regenintensiteit |
[L/T] |
[mm/hour] |
\(K_u\) |
Empirical coefficient, equal to 6.92 |
Empirische coëfficient, gelijk aan 6.92 |
[-] |
|
\(k\) |
Reservoir coefficient |
Reservoircoëfficiënt |
[L\(^3\)] |
|
\(l\) |
Length of a flow segment |
Lengte van een stroomsegment |
[L] |
|
\(m\) |
Bank slope denominator: horizontal distance for a vertical displacement of 1 |
Noemer van de oeverhelling: horizontale afstand voor een verticale verplaatsing van 1 |
[L/L] |
|
\(N\) |
Number of years of measurement |
aantal gemeten jaren |
[-] |
|
\(n_m\) |
Manning roughness coefficient |
Ruwheidscoëfficient van Manning |
[T/L\(^{1/3}\)] |
|
\(P\) |
Precipitation |
Neerslag |
[L/T] |
|
\(P_w\) |
Wetted perimeter of the watercourse |
Natte omtrek van de waterloop |
[L] |
|
\(P_a\) |
Effective precipitation (also: Net precipitation, Stormflow-generating precipitation) |
Afvoerbare neerslag (ook: Effectieve neerslag, Netto neerslag, Overtollige neerslag) |
[L/T] |
|
\(p\) |
Probability of exceedance (\(p\) = Pr(\(X>x\))) |
Kans op overschrijding |
[1/T] |
|
\(Q\) |
Runoff (Often expressed per unit area) |
Afvoer (Vaak uitgedrukt per eenheid van oppervlak) |
[L/T] |
|
\(Q\) |
Discharge (also: Streamflow) |
Debiet |
[L\(^3\)/T] |
|
\(Q_T\) |
Discharge return level |
Terugkeerniveau van de piekafvoer |
[L\(^3\)/T] |
|
\(q\) |
Probability of non-exceedance (\(q\) = Pr(\(X \leq x\))) |
Kans op onderschrijding |
[1/T] |
|
\(R\) |
Hydraulic radius |
Hydraulische straal |
[L] |
|
\(S\) |
Storage |
Berging |
[L\(^3\)] |
|
\(s\) |
Energy slope in the flow direction (in uniform flow, equal to bed slope or water surface slope) |
Helling in de stroomrichting |
[L/L] |
|
\(T\) |
Return period |
Herhalingstijd |
[T] |
[year] |
\(t_c\) |
Time of concentration |
Looptijd |
[T] |
[min] |
\(t_{ocf}\) |
Travel time for the open-channel flow segment(s) |
Duur van afstroming in open waterlopen |
[T] |
[min] |
\(t_{osf}\) |
Travel time for the sheet flow segment |
Duur van afstroming over oppervlakte |
[T] |
[min] |
\(t_{pf}\) |
Travel time for the pipe flow segment(s) |
Duur van afstroming door buizen |
[T] |
[min] |
\(t_{scf}\) |
Travel time for the shallow concentrated flow segment |
Duur van ondiepe geconcentreerde stroming |
[T] |
[min] |
\(v\) |
Flow velocity |
Stroomsnelheid |
[L/T] |
|
\(y\) |
Reduced variate |
Gereduceerde variaat |
[-] |
Note
\(Q\) in this chapter - as well as in engineering hydrology practice - is also simply used for various specific parts of the flow/discharge/runoff, such as storm flow, peak flow or base flow, although a subscript would have been more appropriate.