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).