This report investigates the relationship between the degree of imperviousness – surface sealing – and the water balance – surface runoff, evapotranspiration and infiltration. It synthesizes case studies for the cities Leipzig, Dessau and Munich in Germany and the Grote-Nete catchment in Belgium and compares the effect of different urban land uses on the water balance. The annual precipitation ranges from 530 to 950 mm. Depending on the respective hydrological properties and land use characteristics a linear increase of surface runoff with increasing degree of imperviousness could be found for all of the German studies. Evapotranspiration and infiltration decline with an increasing degree of imperviousness. The relationship for both is not distinct as for surface runoff. The impact on the water balance does not significantly deviate for different levels of precipitation.
Table of Contents
1. Introduction
1.1 Areas of study
2. Methods
2.1 Calculation of the water balance
2.2 Matching of different studies by degree of imperviousness
2.3 Estimation of the relationship of the water balance and degree of imperviousness
3. Results
4. Discussion
5. Conclusion
Objectives & Research Topics
This report examines the correlation between surface sealing (imperviousness) and key water balance components, including surface runoff, evapotranspiration, and infiltration, across different urban environments in Germany and Belgium.
- Impact of urban land use on water balance components
- Analysis of surface sealing levels in relation to precipitation variations
- Empirical verification of runoff increases and infiltration declines
- Comparative case studies of urban areas (Leipzig, Dessau, Munich, Grote-Nete)
- Evaluation of urban planning implications for groundwater and flood risk
Excerpt from the Book
The trade-offs from surface sealing
The trade-offs from surface sealing mainly occur in urbanized areas as they have a higher degree of imperviousness as paved roads or buildings are built much more densely. Especially a decrease of the permeability of the soil increases surface runoff and decreases infiltration. Due to the lower infiltration to recharge the groundwater, groundwater aquifers are not sufficiently recharged anymore and the water table declines (Haase & Nuissl, 2007). The filtering capacity of the soil is only used to a much smaller extent as less water moves through the soil. (Emmerling & Udelhoven, 2002) Due to soil surface sealing, the water storage capacity of the soil - a buffer for the variability of precipitation – can be used less due to hindered infiltration. As a consequence the amplitude between peak and base flow increases and the discharge occurs at different times – more at rainstorm events, less in between. The base flow of receiving surface water bodies such as rivers decreases. This means that the water provision in dry periods is weakened as the soil water cannot contribute to the surface runoff the more the soil is sealed. At peak flows the discharge rate and velocity of surface runoff is increased compared to unsealed soils as sealed soils respond faster to rainstorm events.
Summary of Chapters
1. Introduction: Provides a definition of surface sealing and outlines the problem of increasing urban imperviousness in Europe and its impact on the environment.
1.1 Areas of study: Presents the geographical scope of the research, comparing the size, precipitation levels, and catchment characteristics of the selected cities.
2. Methods: Details the hydrological models used across the different case studies to estimate the water balance components.
2.1 Calculation of the water balance: Explains the specific modeling approaches, such as ABIMO and WetSpass, used to quantify runoff, infiltration, and evapotranspiration.
2.2 Matching of different studies by degree of imperviousness: Describes the methodology for categorizing land use types according to their sealing levels to allow for standardized comparisons.
2.3 Estimation of the relationship of the water balance and degree of imperviousness: Outlines the regression analysis used to determine if runoff and infiltration dependencies are linear.
3. Results: Displays the empirical findings through graphical representations of runoff, infiltration, and evapotranspiration trends.
4. Discussion: Evaluates the consistency of the findings across the studies and addresses potential sources of inaccuracy due to site-specific variables.
5. Conclusion: Summarizes the severe impacts of surface sealing and discusses potential mitigation strategies, such as reducing urban sprawl.
Keywords
Surface sealing, water balance, imperviousness, surface runoff, infiltration, evapotranspiration, urban sprawl, urban planning, groundwater recharge, catchment, hydrological model, land use, flood risk, precipitation, urban environment.
Frequently Asked Questions
What is the core focus of this report?
The report investigates the relationship between the degree of urban surface sealing and the components of the water balance: surface runoff, evapotranspiration, and infiltration.
What are the primary thematic areas?
The central themes include urban hydrology, land use changes, water balance modeling, and the environmental consequences of soil compaction in urbanized landscapes.
What is the central research question?
The study aims to find empirical evidence across multiple cities to determine how increasing imperviousness impacts the water balance and whether these trends remain consistent under different levels of precipitation.
Which scientific methods are applied?
The author synthesizes data from various local studies (using models like ABIMO and WetSpass) and applies regression analysis and t-tests to evaluate the significance of correlations between imperviousness and hydrological variables.
What does the main body of the work cover?
It covers the selection of study areas in Germany and Belgium, detailed descriptions of modeling methods, the comparative analysis of imperviousness degrees, and the presentation of results regarding runoff, infiltration, and evapotranspiration.
Which keywords best characterize this research?
Key terms include surface sealing, imperviousness, water balance, urban sprawl, and groundwater recharge.
Does surface sealing affect the risk of flooding in cities?
Yes, the report demonstrates that increased urbanization and higher degrees of surface sealing lead to faster response times to rainstorm events and increased surface runoff, which significantly raises the risk of flooding.
Are there critical thresholds for infiltration decline?
Findings vary; while the Leipzig study suggests a critical value between 50% and 70% imperviousness for infiltration, other study areas show that even small degrees of sealing can affect infiltration capacity.
How could the negative impacts of sealing be mitigated?
The author suggests reducing urban sprawl as the primary solution, complemented by the use of semi-pervious materials (like lawn bricks or cobblestones) for roads and parking areas.
- Arbeit zitieren
- Markus Meyer (Autor:in), 2011, Surface sealing and the water balance, München, GRIN Verlag, https://www.hausarbeiten.de/document/184670
