Effects of Tree Cover on runoff coefficient depends on relationship between Tree Cover and rainfall

Introduction

The relationship between tree cover and runoff coefficient is a critical aspect of hydrological studies, particularly in the context of varying rainfall patterns. Understanding how tree cover influences runoff can inform land use and flood management strategies, especially as climate change alters precipitation trends.

Key Insights

Impact of Tree Cover on Runoff Coefficient:
- Increased forest cover generally leads to higher runoff coefficients during larger flood events due to higher antecedent soil moisture retention and deeper root zones.
- For smaller flood events, higher forest cover results in lower runoff coefficients due to higher evapotranspiration and soil moisture capacity.
Role of Ground and Canopy Cover:
- Ground cover, especially leaf litter, is more effective in reducing runoff than canopy cover. Canopy cover is more effective during less intense storms but ineffective during high-intensity rainfall.
- A minimum ground cover of 60% can keep runoff within 10% of total rainfall during normal monsoons, reducing the risk of soil erosion and gullying.
Urban Trees and Rainfall Interception:
- Urban trees can significantly reduce runoff by intercepting rainfall. For example, Betula pendula can intercept 20.6% of annual rainfall, while Pinus nigra can intercept up to 51.0%.
- Planting trees in urban areas, such as parking lots, can reduce runoff by up to 17%.
Rainfall Variability and Runoff Generation:
- Rainfall amount and intensity are primary controls of runoff generation. Runoff coefficients are higher for wet antecedent conditions compared to dry conditions.
- In dryland environments, runoff generation is more sensitive to ground cover during drier months, highlighting the critical role of cover at the onset of the wet season.
Land Cover Change and Local Rainfall:
- Changes in tree cover can impact local rainfall patterns. For instance, significant changes in rainfall were observed in a bushfire-affected region in Australia due to changes in tree cover.
- However, in regions with high rainfall variability and possible regrowth, the impact of tree cover change on rainfall may not be statistically significant.

Conclusion

The relationship between tree cover and runoff coefficient is complex and influenced by various factors, including the size of flood events, ground and canopy cover, and antecedent soil moisture conditions. Increased forest cover can lead to higher runoff coefficients during larger flood events but lower coefficients during smaller events. Ground cover plays a crucial role in reducing runoff, especially during less intense storms. Urban trees can effectively intercept rainfall and reduce runoff in urban areas. Additionally, changes in tree cover can impact local rainfall patterns, although this effect may vary depending on regional conditions. Understanding these dynamics is essential for effective land use and flood management.

Effects of Tree Cover on runoff coefficient depends on relationship between Tree Cover and rainfall

Summary

Introduction

Key Insights

Conclusion

Sources and full results

Effects of land cover on runoff coefficient

High forest cover increases runoff coefficient during larger flood events, but offers flood mitigation benefits for smaller flood events, with different effects on smaller and larger flood events.

Can Urban Trees Reduce the Impact of Climate Change on Storm Runoff

Urban trees can reduce the impact of climate change on storm runoff by intercepting up to 51% of annual rainfall, effectively reducing storm water volumes and costs.

Relationships between runoff and land degradation on non-cultivated land in the Middle Hills of Nepal

A minimum ground cover of 60% can reduce runoff to within 10% of total rainfall amounts in the Middle Hills, reducing the risk of gullying and surface soil erosion.

Characterisation of hydrological response to rainfall at multi spatio-temporal scales in savannas of semi-arid Australia

Rainfall amount and intensity significantly control runoff generation processes in dryland environments, with ground cover playing a critical role in drier months and affecting coral reef ecosystems.

Detecting the impact of land cover change on observed rainfall

Changes in tree cover can cause significant changes in rainfall, but in some areas, such as Queensland, the impact is not strong enough to warrant further investigation.

Rainfall redistribution beneath an olive orchard

Rainfall redistribution beneath olive orchards can significantly affect water supply for trees in dry years, and considering these differences in infiltration patterns is crucial for designing conservation strategies.

Scale dependence of Hortonian rainfall‐runoff processes in a semiarid environment

Rainfall-runoff processes in semiarid environments decrease with increasing scale, with run-on infiltration playing a major role, but rainfall intensity and soil properties can also affect the scaling trend.

Forest cover influence on regional flood frequency assessment in Mediterranean catchments

Forest cover significantly influences regional flood frequency assessments in Mediterranean catchments, particularly in small mountainous areas with large forest cover and lower critical rainfall depths.

Analysis of the effects of soil management on runoff generation in olive orchards using a physically based model.

No-till and dense cover crops in olive orchards reduce runoff, while no-till and dense cover crops increase it, with tree canopy size having less impact.

Runoff reduction from extensive green roofs having different substrate depth and plant cover

Deeper substrates (16 cm) combined with Origanum onites vegetation cover and lower initial substrate moisture levels significantly reduce runoff from shallow green roof systems.

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