Monitoring and statistical modelling of the solids accumulation rate in gully pots

Figures & data

Figure 1. (a) Measurement device for the sediment bed depth; (b) Gully pot; (c) Side view of sediment bed depth measurement in gully pot.

Table 1. Model parameters.

Parameter	Calculation	Data source
Parameters related to build-up of solids
Connected area	The eight-direction flow approach (Jenson and Domingue (1988)) to determine the size of the paved area connected to a gully pot	Digital elevation data of The Hague (from 2014) from AHN3 (Van der Zon (2013) and from similar dataset owned by the municipality for Rotterdam (from 2016).
Vegetation factor		Datasets from the municipalities of The Hague and Rotterdam containing tree locations and heights.
Tree phase	Classification	Visual observation
Traffic intensity	Numbers copied from the model and for streets not included in the model, estimation based upon surrounding streets with similar traffic conditions.	Traffic model (Het Samenwerkingsorgaan Holland Rijnland (2015)).
Pavement type	Classification	Visual observation
Commercial area	Classification	Visual observation
Street sweeping frequency	Estimation based upon data of ~1 year.	Tracking data of street sweepers from The Hague and time sheets from Rotterdam.
Parameters related to the wash-off of solids
Rainfall intensity	Maximum rainfall intensity in 5-minute interval during the measurement period.	Rain radar KNMI
Rainfall volume	Mean rainfall per day during the measurement period.	Rain radar KNMI
Antecedent dry period	The number of dry days prior to the measurement period, while a day is considered dry when the rainfall intensity stays lower than 1 mm/hour in each 5-minute time slot.	Rain radar KNMI
Parameters related to the retention of solids
Discharge	Maximum rain intensity multiplied by the connected area (Tables 1 and 2).	Rain radar KNMI and digital elevation data.
Cross-sectional area	-	Measured with measuring tape
Inlet type	Classification	Visual observation
Sand trap depth	-	Measured with measurement device
Sediment bed depth	-	Measured with measurement device
Filling degree	Sediment bed depth divided by the sand trap depth.	Measured with measurement device

Table 2. Type of relations between the parameters and the accumulation rate in gully pots. Positive correlations are denoted with a plus sign and negative correlations with a minus sign.

	Dataset 1		Dataset 2
Parameter	RT	LMM	RT	LMM
Connected area	No relation	+	+	+
Vegetation factor	+	+	+	+
Leaf abscission	No relation	+	+	+
Leafless	No relation	-	-	-
Leaf growth	No relation	-	+	-
Full capacity	No relation	-	-	-
Traffic intensity	No relation	No relation	No relation	No relation
Pavement type (asphalt)	No relation	No relation	No relation	+
Commercial area	No relation	No relation	No relation	No relation
Street sweeping	No relation	No relation	+	No relation
Rainfall volume	±	+	±	+
Rainfall intensity	-	No relation	-	No relation
Antecedent dry period	No relation	-	+	+
Discharge	No relation	-	+	-
Cross-sectional area	No relation	No relation	+	No relation
Top inlet	No relation	+	No relation	+
Filling degree	-	-	±	-

Figure 3. RT for dataset 1. The values at the nodes are the number of observations in the group and the mean accumulation rate of the group.

Figure 2. Sediment bed depth development over time in 4 gully pots, which restarts after cleaning.

Jenson, S. K., and J. O. Domingue. 1988. “Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis.” Photogrammetric Engineering and Remote Sensing 54 (11): 1593–1600.

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Van der Zon, N. 2013. Kwaliteitsdocument AHN2 [Quality Document AHN2]. Amersfoort: Rijkswaterstaat & Waterschappen.

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Het Samenwerkingsorgaan Holland Rijnland. 2015. Actualisatie En Harmonisatie Van Het Verkeersmodel Holland Rijnland [Update and Harmosation of the Holland Rijnland Traffic Model]. Leiden: Holland Rijnland.

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