1.2 Integration of hydrological and socio-economic connectivity
concepts in land management plans
Interventions to reduce overland flow and soil erosion by water range in
spatial scale from the farm plot to hillslope and catchment level. The
conservation agriculture (CA) approach (International Institute of Rural
Reconstruction and African Conservation Tillage Network., 2005; Kassam
et al., 2019) centres around the mitigation of on-site soil erosion
effects on cultivated land, where soil conserving cropping practices
help reduce erosion and water run-off. Three key interventions that are
essential to CA, however, are applied to different extents and
site-specific contexts. First, minimum or no-tillage practice reduces
soil disturbance, supports higher infiltration capacity and reduces the
risk of overland flow. Second, permanent cover of soil by vegetation
and/or use of crop residues as mulch reduces rain splash and
compaction/crusting of the soil surface. Third, crop rotations and
intercropping, even though their main aim is to increase soil fertility
and yield, consequentially improve soil organic matter content, increase
soil aggregate stability and hence help reduce erodibility. Edge-of-plot
attenuation features (e.g. vegetative barriers, ditches, bunds, buffers)
mitigate both on-site impacts, through retention and capture of soil and
nutrients in the farm, and off-site impacts, by impeding downslope water
flow. East-African hillslope farms are often cultivated under
slow-forming terraces (Kagabo et al., 2013), where soil eroded up the
plot congregates at the plot boundary, thereby reducing hillslope
gradient. Downslope catchment measures include the use of check dams or
other flow retardants in gullies and incised channels to slow down the
water discharge response to the drainage network, recue channel incision
and stimulate sediment deposition. These offer win-win outcomes of
landscape restoration and enhanced resilience to future climate threats
such as extreme rainfall and drought. Successful implementation of these
multi-scalar intervention opportunities can only be realised with a
thorough and nuanced understanding of community-specific needs and
priorities, as well as wider political and economic contexts, all set
within a deep understanding of landscape hydrological processes and
concepts in both ‘structural’ and ‘process’ connectivity (Bracken et
al., 2013). In brief, the term ‘structural connectivity’ has been used
to describe the distribution of landscape units and features e.g.
topographic controlled, flow convergence lines, gully or track networks
that physically facilitate water and sediment transfers from hillslope
to channel. Structural connectivity approaches are limited to supporting
inferences of potential hydrological connectivity should overland flow
be generated. In this regard, the concept of ‘process connectivity’ has
greater relevance to tackling overland flow generation and soil erosion
by water. This concept encompasses the actual processes that operate to
produce fluxes of water and sediment and capture the evolutionary
dynamics of how hydrological systems function (Bracken et al., 2013).
For example, soil crusting reduces infiltration capacity leading to
infiltration excess overland flow which converges to form and feed rill
and gully network structures. The concept refers to the activation of
the potential pathways described within a structural connectivity
framework, which is generally highly temporally discrete. To date,
however, process and functional connectivity concepts in hydrology have
not directly accounted for the human dimension in land management
decision making an impact of soil hydrology nor the maturity of land
conversion features that might over time increase soil retention
efficacy. Furthermore, in the East African context, connectivity within
hillslopes and river basins is dynamic in both space and time (Wynants
et al., 2020) with marked changes in connectivity due to rainfall
variations, river networks, rapid land use change and positive feedback
of gully incision and channel network expansion over decadal scales -
hydro-geomorphic processes that are still not well understood or
quantified.
The complex spatial and temporal dynamics of overland flow, soil erosion
and sediment conveyance downstream can be better understood by the
scientific community within the framework of hydrological connectivity.
However, stakeholders also have context-specific local in-depth
knowledge of landscape processes, albeit generally through an
agro-pastoral practitioner lens that encompasses social and economic
facets (Wynants et al. 2019). As such, integrating scientific findings
into locally led land management plans presents a challenge/barrier to
research impact. Co-design of land management policy which integrates
local socio-economic and environmental knowledge and is tailored to the
needs of specific communities is a credible pathway to sustainable
change.
Participatory research in this context aims to evaluate not only the key
environmental challenges affecting communities but also, and more
critically, to understand the socio-ecological connectivity (Berkes et
al., 2000) between these environmental challenges and their integration
in socio-economic processes at multiple spatial levels and temporal
scales. Prior work has shown that understanding the linkages is vital to
enable sustainable and equitable change and break the cycle of declining
resilience to soil erosion (Pretty, 1995). In this East African context,
soil erosion is a civic as well as a practical problem. Roads, trackways
and community spaces are all exposed soil surfaces and thus the problem
is not limited to those engaged in agriculture alone; it is a challenge
for the whole community. From this perspective, every community member
has a stake in contributing to the effort to find sustainable solutions;
and every community member has an opportunity to take action to effect
real and lasting change. Co-designing mitigation strategies with
communities ensures that potential solutions are relevant, applicable
and achievable, particularly where alternative livelihood strategies to
support pathways to sustained change are applied. This is exemplified by
Reed et al.’s ‘bottom-up’ participatory principles (Reed et al., 2017)
where community-led planning is guided by the local ambitions of
stakeholders alongside the strategic objectives of external agencies and
state authorities, leading to equitable solutions with much wider
community ‘buy-in’ than those designed through top-down and
non-participatory mechanisms (Pretty, 2003).