Topographic reconstruction: a geomorphic approach

doi:10.1016/j.ecoleng.2004.12.014

Ecological Engineering

Volume 24, Issues 1–2, 30 January 2005, Pages 29-35

https://doi.org/10.1016/j.ecoleng.2004.12.014 Get rights and content

Abstract

The landscapes manufactured during disturbed-land reclamation are the foundations for all subsequent reclamation practices and the surfaces for future land uses. From a geomorphic perspective, the goal of topographic reconstruction is the creation of steady-state landscapes. As the reconstructed drainage basins, hillslopes, and stream channels approach steady-state configurations, adjustments by geomorphic processes after reclamation decrease. As the adjustments necessary to establish the steady state decrease, the prospect for reclamation success increases and the demand for post-reclamation site maintenance decreases. Digital elevation modeling software offers an opportunity to incorporate geomorphic principles into topographic reconstruction at the design stage of reclamation. As a first approximation, drainage-basin area, weighted mean slope, and drainage density for the pre-disturbance or undisturbed landscape are closely replicated in the reconstructed topography. The technical and economic feasibility of this approach is currently being tested.

Introduction

Under natural conditions, geomorphic processes usually sculpt the land surface of the earth into drainages basins, each of which is composed of hillslopes and stream channels. These drainage basins function as open, process-response systems for the efficient transportation of water and sediment. Changes in water and sediment inputs result in changes in water and sediment outputs, sometimes with concomitant changes in the morphologic characteristics of hillslopes and stream channels to the extent necessary to maintain efficient operation of the systems.

Under natural conditions, an approximate steady-state or dynamic equilibrium prevails within drainage-basin systems. With approximate balances among forces and resistances, geomorphic processes operate at low rates. Hence, changes in morphologic characteristics are slow over long time periods as often demonstrated by photographs of the same landforms taken decades apart. There is no on-site or off-site degradation of the environment as long as the steady-state prevails.

Disturbances to the steady-state of drainage-basin systems result in various imbalances among forces and resistances, causing geomorphic processes to operate at accelerated rates. These processes may work to re-establish the previous steady-state, with morphologic characteristics of hillslopes and stream channels that are similar to those of the past. Alternatively, the processes may work to establish a new steady-state, with new morphologic characteristics of hillslopes and stream channels. During this period of adjustment and accelerated process rates, drainage-basin surfaces experience mass-instability and dissection by erosion processes. Large amounts of sediment are produced, transported off-site, and deposited in streams, lakes, and reservoirs. On-site and off-site environmental degradation occurs rapidly, and collectively may affect areas many times the size of initial land disturbance. Eventually, geomorphic processes restore a steady-state, but this may take hundreds of years.

Section snippets

Geomorphic goals for land reclamation

From a geomorphic perspective, the goal of topographic reconstruction is a steady-state landscape with approximate balances among forces and resistances. These landscapes are composed of drainage basins again functioning as open process-response systems with efficient flow of water and sediment, geomorphic processes operating at low rates, no on-site or off-site environmental degradation, and are capable of sustaining productive post-reclamation land uses.

Unfortunately, it is not possible to

The reclamation process

The reclamation process consists of 10 sequential steps: (1) site characterization, (2) reclamation planning and engineering, (3) material management, (4) topographic reconstruction, (5) replacement of topsoil or soil substitute, (6) surface manipulation, (7) addition of soil amendments, (8) revegetation, (9) irrigation, if needed, and (10) site monitoring and maintenance (Toy and Daniels, 2000). Topographic reconstruction is an essential part of high-quality reclamation because the resulting

Drainage-basin design

The design of steady-state drainage basins begins by locating the main channel through the reclaimed area. The position of this channel is determined by the topography of adjacent, undisturbed areas and the overall, post-reclamation topography of the disturbed land. Then, drainage networks for the reclaimed areas are designed with dendritic drainage patterns and sufficient drainage densities to accommodate the anticipated water and sediment discharges through the reclaimed area. Drainage

A geomorphic approach

Digital elevation modeling software offers the opportunity to incorporate geomorphic principles into topographic reconstruction during the planning and design stages of reclamation. A small coal mine in southcentral Colorado, USA, was selected for our initial efforts to develop design procedures because topographic maps, aerial photographs, and a digital elevation model are available for this site as shown in Fig. 2. The first step is geomorphic analyses of the pre-disturbance landscape to

Conclusion

Topographic reconstruction is a critical part of the reclamation process because the resulting landscapes are the foundation for all other reclamation practices and the surfaces for future land uses. From a geomorphic perspective, the goal of topographic reconstruction is the creation of steady-state landscapes. Other reclamation goals cannot be achieved if the surface experiences accelerated mass-movement and erosion rates.

Digital elevation modeling software facilitates the incorporation of

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Mining is of interest to geomorphologists because of the unique types of excavated and accumulated landforms and landscapes that are vulnerable to geomorphic hazards. Mining is extensive worldwide. It produces more sediment than paved road construction, house construction or agriculture. Mining is associated with increasing vulnerability to slope failures, erosion, floods, sedimentation, subsidence, and other geomorphic hazards. Understanding and effectively applying geomorphic principles are important for preventing or minimizing the negative effects of mining. This chapter discusses the types and history of mining operations and associated geomorphic impacts that may result in characteristic landforms and landscapes. It then describes mining-related geomorphic hazards and the nascent fields of sustainable mining and mined-land reclamation. We have much still to learn from the study of mining landscapes, with potential applications in landscape evolution, models of geomorphic hazards, reclamation, and Quaternary geology and geomorphology. Given a growing global population and expanding demands for mineral resources, the need for sustainable practices will increase and wise application of geomorphic knowledge in mined landscapes will become increasingly important.
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Citation Excerpt :
Geomorphic restoration, still a young discipline, is a solution that helps solving these problems. During geomorphic restoration, the landscape is designed and shaped to mimic both the look and —most importantly— the functionality of nature (Toy and Chuse, 2005; OSMRE, 2019). This provides the foundation on which, after proper soil and vegetation restoration, the ecosystem goods and services of our life-support systems can be firmly re-established.
This research documents the successful application of a novel holistic approach to return land degraded over thousands of years of use to full ecological function. The surroundings of the Somolinos hamlet in Central Spain illustrate a millennial history of land transformation and degradation by agrarian and extractive activities exacerbated at the second half of the 20th century by mechanized mining. This land stewardship history was culminated by a recent intervention of geomorphic-based ecological restoration and its monitoring.
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One of the main purposes of this research was to carefully scrutinize the completed project, to evaluate its effectiveness and, if any deficiencies were found, to analyze their causes, so that they could be avoided in the future. Therefore, the landscape evolution and erosional behaviour of the restored area has been monitored from 2011 to 2020 through a time-lapse sequence of several oblique aerial photos, and by comparing topographies through Digital Elevation Models (DEMs) of Difference (DoDs). Those topographies were surveyed with differential GPS (DGPS) and with Structure from Motion (SfM) combined with Unmanned Aerial Vehicles (UAVs). This monitoring revealed: (a) landscape healing and diversification of the vegetation community composition and structure, as a result of the environmental heterogeneity of the geomorphic design; and (b) absence of hillslope and channel erosion for 99.8% of the area with limited surface erosion zones in 0.2% of the restored area.
Our analysis attributed those limited erosion zones to a combination of: (a) minor design oversights; (b) slight construction deviation from the design grade; and (c) excessive runoff entering the repaired area that exceeded the design discharge. These erosion zones started to stabilize five years after initial restoration and achieved steady-state stability at nine years.
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Topographic reconstruction: a geomorphic approach

Abstract

Introduction

Section snippets

Geomorphic goals for land reclamation

The reclamation process

Drainage-basin design

A geomorphic approach

Conclusion

The drainage basin as the fundamental geomorphic unit

Sources of soil eroded by water from upland slopes

Present and Prospective Technology for Predicting Sediment Yields and Sources.

Process Geomorphology

The Fluvial System