The Stormwater Experts

Storm Water Management Maps

The potential of decentralized stormwater management in urban areas depends on many factors (see figure). To get a better overview, how much SUDS potential is available and which technique is the best, Storm Water Management Maps for the complete area of cities can be realized. Consequently, a systematic inventory and classification of relevant factors is most of the times extremely useful. It is the basis of which a deployment of decentralized stormwater management systems can be tested and evaluated. With Geographic Information Systems, a GIS-based planning can be carried out, if sufficiently data material is available.

Criteria effecting SUDS potential

The implementation of potential decentralized rainwater measures in a area is represented by two different maps: the first map is called "stormwater management systems map" and is characterizes by the features of considered decentralized stormwater management systems.

The second map is called "Map of decoupling potential". It is used to identify, analyze, and evaluate the potential for implementing management measures for various plots within the site. The representation of the disconnection potential is as a percentage value.

Stormwater management Map

The stormwater management map implementation offers limitless possibilities to classify the different decentralized stormwater management measures as a function of corresponding natural factors.

Depending on biological, morphological, topographical and geological factors, baselines are proposed for an optimal system. They range from simple surface infiltration to networked and combined seepage systems for groundwater management.

The criteria for creating a stormwater management map are based on the classified and superimposed factors affecting considered measures.

Additional factors are the soil water balance, depth to groundwater, contaminated sites or the distance to the aquatic environment.

Methodology creating Map of SUDS technique 

Not all stormwater management measures are dependent on geogenic factors (eg green roof). These measures can basically be implemented everywhere, unless additional factors are influencing the system implementation (eg statics of the roof).

Map of disconnection potential

For breaking the direct connections between impervious areas and conventional drainage network systems the decoupling potential map presents a quantitative analysis and evaluation of disconnection.

The potential of decoupling is mostly based on the plot situation within the masterplan.

The work methodology for determining rainwater disconnection potential is divided into three steps:

  1. Determination and classification of buildings
  2. Assessment of individual areas
  3. Analysis of digital maps for determining the decoupling potential

To classification of buildings is done as per the following criteria:

  • Prevailing number of floors

  • Building structure (single house, doubles, etc.)

  • Design type (open, closed)

  • Open space surface

  • Usage (industrial, commercial, residential, public)

  •  area size

The assignment of the building structure is done using Geographical Information Systems (GIS).

Figure 3: Land classification

Classification of similar building structures

Estimation of the decoupling potential requires on on-site inspections. Neighboring properties, density of the urban areas, landscape area... Several factors should be investigated.

Result of mapping for a selected area

The following items must be verified for mapping:

  • Position of downpipe (where decentralized systems are proposed)
  • Location and size of trees (influencing the locations of facilities)
  • Gullies
  • Potential open spaces for RW measures
  • Degree of the sealed surfaces
  • Roof shape (technical difficulty for the decoupling capture)
  • Slope (direction of water flow)

Excerpts consist of the following:

Assessment of building structures for SUDS suitability

Creating the map

In addition to structure classification additional factors for finalizing decoupling potential must be investigated and corrected. Slope direction, location of unpaved and paved surface…affects the potential given value.

Assessment of criteria effecting disconnection potential

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Dipl.-Geogr. Stephan Bandermann
+49 3342 3595-14