Chapter 13
Tunnel Flow and Erosion Processes
in an Experimental Catchment
Abstract Soil pipes and tunnels have been reported in a wide range of climatic
conditions in the world, yet their hydrological and sediment processes have been
much understudied in comparison with surface flows. In this chapter, storm flows
and sediment processes were monitored at 6 tunnel systems in an experimental catchment in the Loess Plateau. The results indicate that all the tunnel flow was derived
from overland flow entering via inlets. However, both flow discharges and sediment
concentrations were highly erratic due to the instability of tunnel systems. Tunnels could be clogged by collapse inside, which reopened in subsequent events. An
intensive storm could develop new inlet(s), which either joined the existing tunnel
system or started a new one. Partial damming within the tunnel systems also frequently occurred. This chapter showed that at least 43% of water flows and 57% of
sediments were routed via tunnels in the experimental catchment.
Keywords Tunnel systems · Hydrological processes · Sediment processes ·
Tunnel instability · Contributions to catchment
13.1 A Brief Introduction on the Tunnel Erosion
Soil pipes or tunnels have been reported in many parts of the world, including Europe
(Verachtert et al. 2010; Piccarreta et al. 2006; Holden 2005; Faulkner et al. 2004;
Jones 1987; Harvey 1982), North America (Wilson et al. 2015; Seppälä 1997; Parker
et al. 1990; Swanson et al. 1989; Drew 1982; Heede 1971; Parker and Jenne 1967),
Asia (Zhu 2003; Onda 1994), Australia (Crouch et al. 1986) and Africa (Frankl
et al. 2016; Boucher and Powell 1994; Dardis and Beckedahl 1988; Yair et al. 1980).
Soil piping/tunnel erosion has been increasingly recognized as a significant hillslope
hydrological and geomorphologic process (Carey and Woo 2000; Uchida et al. 1999;
Zhu 1997; Bryan and Jones 1997; Jones and Bryan 1997; Walsh and Howells 1988;
Crouch et al. 1986; Bryan and Harvey 1985; Wilson and Smart 1984; McCaig 1983;
Jones 1981; Gilman and Newson 1980). However, quantitative studies on pipe-flow
and erosion processes are generally very limited and most of these studies have been
conducted in humid areas (Walsh and Howells 1988; Jones 1987, Jones 1981; Jones
and Crane 1984; McCaig 1983; Gilman and Newson 1980), and comparatively few
© Science Press and Springer Nature Singapore Pte Ltd. 2020
X. Xu et al., Experimental Erosion,
https://doi.org/10.1007/978-981-15-3801-8_13
209
Tunnel Flow and Erosion Processes
in an Experimental Catchment
Abstract Soil pipes and tunnels have been reported in a wide range of climatic
conditions in the world, yet their hydrological and sediment processes have been
much understudied in comparison with surface flows. In this chapter, storm flows
and sediment processes were monitored at 6 tunnel systems in an experimental catchment in the Loess Plateau. The results indicate that all the tunnel flow was derived
from overland flow entering via inlets. However, both flow discharges and sediment
concentrations were highly erratic due to the instability of tunnel systems. Tunnels could be clogged by collapse inside, which reopened in subsequent events. An
intensive storm could develop new inlet(s), which either joined the existing tunnel
system or started a new one. Partial damming within the tunnel systems also frequently occurred. This chapter showed that at least 43% of water flows and 57% of
sediments were routed via tunnels in the experimental catchment.
Keywords Tunnel systems · Hydrological processes · Sediment processes ·
Tunnel instability · Contributions to catchment
13.1 A Brief Introduction on the Tunnel Erosion
Soil pipes or tunnels have been reported in many parts of the world, including Europe
(Verachtert et al. 2010; Piccarreta et al. 2006; Holden 2005; Faulkner et al. 2004;
Jones 1987; Harvey 1982), North America (Wilson et al. 2015; Seppälä 1997; Parker
et al. 1990; Swanson et al. 1989; Drew 1982; Heede 1971; Parker and Jenne 1967),
Asia (Zhu 2003; Onda 1994), Australia (Crouch et al. 1986) and Africa (Frankl
et al. 2016; Boucher and Powell 1994; Dardis and Beckedahl 1988; Yair et al. 1980).
Soil piping/tunnel erosion has been increasingly recognized as a significant hillslope
hydrological and geomorphologic process (Carey and Woo 2000; Uchida et al. 1999;
Zhu 1997; Bryan and Jones 1997; Jones and Bryan 1997; Walsh and Howells 1988;
Crouch et al. 1986; Bryan and Harvey 1985; Wilson and Smart 1984; McCaig 1983;
Jones 1981; Gilman and Newson 1980). However, quantitative studies on pipe-flow
and erosion processes are generally very limited and most of these studies have been
conducted in humid areas (Walsh and Howells 1988; Jones 1987, Jones 1981; Jones
and Crane 1984; McCaig 1983; Gilman and Newson 1980), and comparatively few
© Science Press and Springer Nature Singapore Pte Ltd. 2020
X. Xu et al., Experimental Erosion,
https://doi.org/10.1007/978-981-15-3801-8_13
209